1、Designation: D7648 12Standard Practice forActive Soil Gas Sampling for Direct Push or Manual-DrivenHand-Sampling Equipment1This standard is issued under the fixed designation D7648; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, t
2、he year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice details the collection of active soil gassamples using a variety of sample collection techniq
3、ues withtooling associated with direct push drilling technology (DPT)or manual-driven hand-sampling equipment, for the expresspurpose of conducting soil gas surveys.1.2 This practice proceeds on the premise that soil gassurveys are primarily used for two (2) purposes, 1) as apreliminary site investi
4、gative tool and 2) for the monitoring ofongoing remediation activities.1.3 The practicality of field use demands that soil gassurveys are relatively accurate, as well as being simple, quick,and inexpensive. This guide suggests that the objective of soilgas surveys is linked to three factors:1.3.1 VO
5、C detection and quantitation, including determina-tion of depth of VOC contamination.1.3.2 Sample retrieval ease and time.1.3.3 Cost.1.4 This practice will likely increase the awareness of afundamental difference between soil gas sampling for thepurpose of soil gas surveys versus sub-slab or vapor i
6、ntrusioninvestigations or both. Specifically, the purpose of a soil gassurvey is to provide quick and inexpensive data to theinvestigator that will allow the investigator to 1) develop a siteinvestigation plan that is strategic in its efforts, 2) determinesuccess or progress of on-going remedial act
7、ivities, or 3) selectthe most suitable subsequent investigation equipment, or com-binations thereof. On the other hand, the objective of soil gassampling for sub-slab and vapor intrusion investigations (1, 2,3,2etc.) is not preliminary, but rather the end result of the siteinvestigation or long-term
8、 precise monitoring. As such, strin-gent sampling methods and protocol are necessary for precisesamples and data collection.1.5 Details included in this practice include a broad spec-trum of practices and applications of soil gas surveys, includ-ing:1.5.1 Sample recovery and handling,1.5.2 Sample an
9、alysis,1.5.3 Data interpretation, and1.5.4 Data reporting.1.6 This practice suggests a variety of approaches useful toconducting successful soil gas surveys but cannot replaceeducation or experience and should be used in conjunction withprofessional judgment. Not all aspects of this practice may bea
10、pplicable in all circumstances. This ASTM standard is notintended to represent or replace the standard of care by whichthe adequacy of a given professional service must be judged,nor should this document be applied without consideration ofa projects many unique aspects.1.7 This practice offers an or
11、ganized collection of informa-tion or a series of options and does not recommend a specificcourse of action. The success of any one soil gas surveymethodology is strongly dependent upon the environment inwhich it is applied.1.8 This practice is not to be used for long term monitoringof contaminated
12、sites or for site closure conformation.1.9 This practice is not to be used for passive determinationof flow patterns at contaminated sites.1.10 This practice does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this practice t
13、o establish appropri-ate safety and health practices and determine the applicabilityof regulatory limitations prior to use.1.11 This practice does not purport to set standard levels ofacceptable risk. Use of this practice for purposes of riskassessment is wholly the responsibility of the user.1.12 C
14、oncerns of practitioner liability or protection from orrelease from such liability, or both, are not addressed by thispractice.2. Referenced Documents2.1 ASTM Standards:3D653 Terminology Relating to Soil, Rock, and ContainedFluids1This practice is under the jurisdiction of ASTM Committee D18 on Soil
15、 andRock and is the direct responsibility of Subcommittee D18.21 on Groundwater andVadose Zone Investigations.Current edition approved March 1, 2012. Published April 2012. DOI: 10.1520/D7648-12.2The boldface numbers in parentheses refer to a list of references at the end ofthis standard.3For referen
16、ced 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West C
17、onshohocken, PA 19428-2959, United States.D1356 Terminology Relating to Sampling and Analysis ofAtmospheresD1357 Practice for Planning the Sampling of the AmbientAtmosphereD1452 Practice for Soil Exploration and Sampling byAugerBoringsD3249 Practice for General Ambient Air Analyzer Proce-duresD3614
18、Guide for Laboratories Engaged in Sampling andAnalysis of Atmospheres and EmissionsD5314 Guide for Soil Gas Monitoring in the Vadose ZoneD6196 Practice for Selection of Sorbents, Sampling, andThermal Desorption Analysis Procedures for Volatile Or-ganic Compounds in Air2.2 EPA Standards:4EPA Method T
19、O-15 Determination Of Volatile OrganicCompounds (VOCs) In Air Collected In Specially-Prepared Canisters And Analyzed By GasChromatography/ Mass Spectrometry (GC/MS)EPA Method TO-17 Determination of Volatile OrganicCompounds in Ambient Air Using Active Sampling OntoSorbent Tubes3. Terminology3.1 Defi
20、nitions of Terms Specific to This Standard:3.1.1 active sampling, na means of collecting an airborneor emission substance that employs a mechanical device suchas a pump or vacuum assisted critical orifice to draw air oremissions onto or through the sampling device.3.1.2 capillary fringe, nthe basal
21、region of the vadosezone comprising sediments that are saturated, or nearly satu-rated, near the water table, gradually decreasing in watercontent with increasing elevation above the water table. Alsosee Terminology D653.3.1.3 contaminant, na material added by human or naturalactivities which may, i
22、n sufficient concentrations, render theatmosphere unacceptable.3.1.4 emplacement, nthe establishment of contaminantresidence in the vadose zone in a particular phase.3.1.5 free product, nliquid phase contaminants releasedinto the environment.3.1.6 free vapor phase, na condition of contaminantresiden
23、ce in which volatilized contaminants occur in porositythat is effective to free and open gaseous flow and exchange,such porosity generally being macroporosity.3.1.7 hot spot, nareas where contaminants exceed cleanupstandards or the highest level at a contaminated site.3.1.8 liquid phase, ncontaminan
24、t residing as a liquid invadose zone pore space, often referred to as “free product.”3.1.9 partitioning, nthe act of movement of contaminantsfrom one soil residence phase to another.3.1.10 semivolatile organic compound (SVOC), nan or-ganic compound with a saturated vapor pressure between10-2kPa and
25、10-8 kPa at 26 C.3.1.11 soil gas, nvadose zone atmosphere.3.1.12 solute phase, na condition of contaminant resi-dence in which contaminants are dissolved in ground water ineither the saturated or the vadose zone.3.1.13 sorbed phase, na condition of contaminant resi-dence in which contaminants are ad
26、sorbed onto the surface ofsoil particles or absorbed by soil organic matter.3.1.14 sorbent, na solid or liquid medium in or uponwhich materials are collected by absorption, adsorption, orchemisorption.3.1.15 sorption, na process by which one material (thesorbent) takes up and retains another materia
27、l (the sorbate) byprocesses of absorption, adsorption, or chemisorption.3.1.16 vadose zone, nthe hydrogeological region extend-ing from the soil surface to the top of the principal water table.3.1.17 volatile organic compound (VOC), nan organiccompound with a saturation vapor pressure greater than 1
28、0-2kPa at 26 C.4. Summary of Guide4.1 Sampling of soil gases (volatile contaminants such asmethane and carbon dioxide, which are indicators of increasedmicrobial activity resulting from organic contaminants) in thevadose zone is an industry-accepted method used to directlymeasure characteristics of
29、the soil atmosphere. Characteristicsdetermined from soil gas sampling are frequently used asindirect indicators of processes occurring in and below asampling horizon, including the presence, composition, originand distribution of contaminants in and below the vadose zone.4.2 Previously, soil gas sam
30、pling was used more as a toolfor laying the groundwork for further soil exploration. Theability to quickly, accurately, and inexpensively determineVOCs, presence, levels, and depths allowed this method tobecome a standard practice for preliminary site investigation aswell as for monitoring the succe
31、ss of on-going site remediationefforts. Currently soil gas sampling has been gaining accep-tance as a reasonable method for the determination of riskassessment of contaminated sites, known as soil gas investiga-tions. This new direction in soil gas sampling is playing amajor role in the development
32、of new methodologies with acurrent trend towards more stringent soil gas sampling methodsand protocols.4.3 However, the practicality of field use demands that thereis a soil gas sampling method that is accurate as well as simple,quick, and inexpensive, for the purposes of preliminary siteinvestigati
33、on and the monitoring of on-going remediationefforts. This guide refers to this method as soil gas survey.4.4 The objective of a soil gas survey is to determine,through relative data, the highest level of contamination at asite (hot spot). Data collected from soil gas surveys providesinformation use
34、ful for the development of strategic and costeffective site investigation plans.4.5 The leading principle behind this guide is that there is adifference between soil gas surveys and soil gas investigations(1, 2, 3).4.6 While the need for stringent methodology is stronglysupported for soil gas invest
35、igations, (sub-slab and vaporintrusion investigations) those same stringent methods and4Available from United States Environmental Protection Agency (EPA), ArielRios Bldg., 1200 Pennsylvania Ave., NW, Washington, DC 20004, http:/www.epa.gov.D7648 122protocols, when used for the purpose of soil gas s
36、urveying, arenot cost effective nor time efficient.4.7 Soil gas surveys need to be more quick, time efficient,and cost effective than soil gas investigation methods. Theeconomic limits coupled with the objective of a soil gas surveymust be the leading factor behind the development of soil gassurvey
37、methodology and protocol. If it takes as much time ormuch money to survey as to investigate, then investigators willnot utilize this tool/practice.4.8 Vadose zone sampling methods have a set of procedures,both general and specific, that must be consistently followed inorder to provide maximum data q
38、uality and usefulness. Soilgas surveys are no exception, with the primary procedurescommon to all soil gas sampling techniques. The proceduresinclude:(1) Planning and preparation,(2) The act of sampling soil gas in the field,(3) Handling and transporting the sample, and(4) This method does not recom
39、mend a sample analysis,interpretation of the results of analysis, nor specific format forthe preparation of a report of findings. Instead it indicatesminimum information to be included in a report of findings.4.8.1 The planning and preparation step begins with theformulation of project objectives, i
40、ncluding purpose of thesurvey, appropriate application of the data to be collected anddata quality objectives.4.8.2 Actual field work consists of recovery of soil gassamples. The method selected should be based upon sitespecific factors and dictated by the project objectives.4.8.3 As samples are bei
41、ng recovered or collected, theymust be handled, field screened, or transported, or combina-tions thereof, in such a way as to assure preservation prior toanalysis.5. Significance and Use5.1 Soil gas is simply the gas phase (air) that exists in theopen spaces between soil particles in the unsaturated
42、 portion ofthe vadose zone. Normally comprised of nitrogen and oxygen,soil gas becomes contaminated when volatile organic com-pounds (VOCs) are released in the subsurface due to spills orleaks, and they begin to evaporate from a fluid phase andbecome part of the soil gas. Over time, VOCs can potenti
43、allymigrate through the soil or groundwater or both and present aproblem to the environment and human health.5.2 Application of Soil Gas SurveysSoil gas surveyingoffers an effective, quick and cost-effective method of detectingvolatile contaminants in the vadose zone. Soil gas surveyinghas been demo
44、nstrated to be effective for selection of suitableand representative samples for other more costly and definitiveinvestigative methods. This method is highly useful at theinitiation of an investigation into the preliminary site investi-gation of determining the existence and extent of volatile orsem
45、ivolatile organic contamination, and determination of lo-cation of highest concetrations, as well as, monitoring theeffectiveness of on-going remedial activities.5.3 Samples are collected by inserting a sampling deviceinto a borehole with hydraulically-driven direct push drillingtechnology or manual
46、ly-driven driven hand sampling equip-ment.5.4 Soil gas surveys can be performed over a wide range ofspatial designs. Spatial designs include soil gas sampling inprofiles or grid patterns at a single depth or multiple depths.Multiple depth sampling is particularly useful for contaminantdeterminations
47、 in cases with complex soil type distribution andmultiple sources. Depth profiling can also be useful in thedetermination of the most appropriate depth(s) at which tomonitor soil gas, as well as the demonstration of migration anddegradation processes in the vadose zone.5.5 Soil gas surveys are used
48、extensively in preliminary siteinvestigations and monitoring of effectiveness of on-going siteremediation efforts. Project objectives must be known and thelimitation of this method considered. Limitations include:5.5.1 Data generated from soil gas surveying is relative andnot of the quality necessar
49、y for a single data set; and5.5.2 Soil gas surveys need to be done quickly, so thismethod is for active soil-gas sampling devices only.6. Apparatus6.1 Soil gas samples are collected by inserting a samplingdevice into an open borehole or telescopically pushed intonative lithology, through other subsurface conduits, with hy-draulically driven direct push drilling technology or manualdriven hand sampling equipment (Figs. 1 and 2). Table 1provides a summary of possible causes of false positive andfalse negative values.6.2 Whether the sampling device is driven by dire
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