1、Designation: D7909 14Standard Guide forPlacement of Blind Actual Leaks during Electrical LeakLocation Surveys of Geomembranes1This standard is issued under the fixed designation D7909; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision
2、, the 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 guide is for placing blind actual leaks in geomem-branes before performing an electrical leak locat
3、ion survey.The geomembranes can be bare (not covered) or can becovered with water or moist soil.1.2 This guide is intended to serve as an additional qualitycontrol/quality assurance (QC/QA) measure to ensure thatleaks through the geomembrane are detectable, site conditionsare proper for leak locatio
4、n surveys, and a valid and completeleak location survey is performed. Because various leaklocation practitioners use a wide variety of equipment toperform these surveys and have a wide range of expertise,placement of blind actual leaks by the owner or ownersrepresentative helps ensure that the leak
5、location survey isbeing performed correctly and completely.1.3 Placing blind actual leaks can also assist in determiningwhether or not the site conditions permit the flow of electriccurrent through leaks, which is necessary for detecting leaksusing electrical methods.1.4 For clarification, this guid
6、e is in addition to the typicalplacement of the artificial or actual leaks placed as described inthe relevant ASTM International standards for the various leaklocation methods.1.5 Placing blind actual leaks should be done with theconsent and knowledge of all involved parties and specificallythe “own
7、er” of the geomembrane. Geomembranes are typicallypurchased and installed by dedicated geosynthetic installerswho “own” the geomembrane until the ownership gets trans-ferred to the end user. A project meeting should be set up withthe owner, the consultant, the geosynthetic installers, and theleak lo
8、cation contractor. The intention to use blind leaks shouldbe clearly stated by the owner or consultants or both and thescope and number to be placed should be understood by allparties. The consultant should broadly identify to the liningcontractor a location that can be easily repaired after the tes
9、t. Itis critical that all actual blind holes be included on the linerdocumentation and repair record drawing.1.6 Leak location surveys can be used on geomembranesinstalled in basins, ponds, tanks, ore and waste pads, landfillcells, landfill caps, and other containment facilities. Theprocedures are a
10、pplicable for geomembranes made of electri-cally insulating materials. (WarningThe electrical methodsused for geomembrane leak location could use high voltagesresulting in the potential for electrical shock or electrocution.This hazard might be increased because operations might beconducted in or ne
11、ar water. In particular, a high voltage couldexist between the water or earth material and earth ground orany grounded conductor. These procedures are potentially verydangerous and can result in personal injury or death. Theelectrical methods used for geomembrane leak location shouldbe attempted onl
12、y by qualified and experienced personnel.Appropriate safety measures shall be taken to protect the leaklocation operators as well as other people at the site.)1.7 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.8 This standard
13、 does not purport to address all of thesafety concerns, 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 limitations prior to use.2. Referenced Documents2.1 ASTM
14、Standards:2D4439 Terminology for GeosyntheticsD6747 Guide for Selection of Techniques for ElectricalDetection of Leaks in GeomembranesD7002 Practice for Leak Location on Exposed Geomem-branes Using the Water Puddle SystemD7007 Practices for Electrical Methods for Locating Leaksin Geomembranes Covere
15、d with Water or Earth Materials1This test method is under the jurisdiction of ASTM Committee D35 onGeosynthetics and is the direct responsibility of Subcommittee D35.10 on Geomem-branes.Current edition approved March 1, 2014. Published March 2014. DOI: 10.1520/D7909142For referenced ASTM standards,
16、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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428
17、-2959. United States1D7240 Practice for Leak Location using Geomembraneswith an Insulating Layer in Intimate Contact with aConductive Layer via Electrical Capacitance Technique(Conductive Geomembrane Spark Test)D7703 Practice for Electrical Leak Location on ExposedGeomembranes Using the Water Lance
18、System3. Terminology3.1 Definitions: For general definitions used in this guide,refer to Terminology D4439.3.2 Definitions of Terms Specific to This Standard:3.2.1 artificial leak, nfor the purposes of this guide, anartificial leak is an electrical simulation of a leak in ageomembrane during the lea
19、k detection sensitivity setup.3.2.2 blind actual leak, nfor the purposes of this guide, ablind actual leak is a circular hole in the geomembraneintentionally placed by the owner or owners representative toensure that the site conditions are suitable for an electrical leaklocation survey and that a v
20、alid electric leak location survey isperformed in a location unknown to the leak location practi-tioner.3.2.2.1 DiscussionA blind actual leak is not a leak used todetermine the leak detection sensitivity parameters.3.2.3 electrical leak location, nmethod that uses electricalcurrent or electrical pot
21、ential to detect and locate leaks inelectrically isolating geomembranes.3.2.4 leak, nfor the purposes of this guide, a leak is anyunintended opening, perforation, breach, slit, tear, puncture,crack, or seam breach in electrically isolating geomembranes.3.2.4.1 DiscussionSignificant amounts of liquid
22、s or solidsmay or may not flow through a leak. Scratches, gouges, dents,or other aberrations that do not completely penetrate thegeomembrane are not considered to be leaks.3.2.5 leak detection sensitivity, nsmallest size leak that theleak location equipment and survey methodology are capableof detec
23、ting under a given set of conditions.3.2.5.1 DiscussionThe leak detection sensitivity specifi-cation is usually stated as a diameter of the smallest leak thatcan be reliably detected.4. Significance and Use4.1 Geomembranes are used as low-permeability barriers tocontrol liquids from leaking from lan
24、dfills, ponds, and othercontainments. The liquids may contain contaminants that, ifreleased, can cause damage to the environment. Leakingliquids can also erode the subgrade. Leakage can result inproduct loss or otherwise prevent the installation from per-forming its intended containment purpose. For
25、 these reasons, itis desirable that the geomembrane have as little leakage aspractical.4.2 Geomembrane leaks can result even when the quality ofthe subgrade preparation, the quality of the material placed onthe geomembrane, and the quality of the workmanship are notdeficient.4.3 Electrical leak loca
26、tion methods are an effective finalquality assurance (QA) measure to locate previously unde-tected leaks in electrically insulating geomembranes. Practicesfor these implementations are contained in Guide D6747 andPractices D7002, D7007, D7240, and D7703.4.4 It is important to realize that the detect
27、ion of leaksdepends not only on the capabilities of the leak locationequipment, procedures, and experience of the leak locationpractitioner but also on local site conditions that are not underthe control of the leak location practitioner. In particular, todetect a leak, there shall be an electrical
28、conduction paththrough the leak and through the materials above and below theleak to allow sufficient electrical current through the leak fordetection. For some site conditions, such as a leak not makingcontact with the subgrade, dry geotextile, or geocompositeabove or below the leak; dry materials
29、above or below the leak;degree of isolation between the materials above and below thegeomembrane; and other factors, may preclude the detection ofleaks. Therefore, the use of a properly placed blind actual leakis also a test of site preparations and conditions.4.5 It is not necessarily proper to con
30、clude that, if a blindactual leak is not detected, a leak location survey, using theproper relevant ASTM International standard, has no validity.Real leaks that have more favorable site conditions and largerleaks may still be detected.4.6 The importance of blind actual leaks is to provide anaddition
31、al measure to assess whether the site conditions areproper for a leak location survey and that the electric leaklocation survey is performed correctly and completely. The useof blind actual leaks provides: (1) a check that the equipmentis operating properly, (2) a test for proper survey coverage, an
32、d(3) a check that all survey data (results) have been assessed toconfirm a proper survey has been done. These all result in ahigh likelihood that significant-sized leaks are detected.5. Procedural Guidance for Placement of Blind ActualLeaks5.1 The fact that blind actual leak(s) will be installed in
33、thegeomembrane, and who will install the blind leak(s), who willsurvey the locations of the blind leak(s), and finally who willrepair the blind actual leaks should be clearly described in theproject specifications and understood by all affected parties soresponsibilities and costs involved are fully
34、 understood by allaffected parties. For the geomembrane leak location survey anduse of blind actual leaks to be decisive, the project specifica-tions should also specify the relevant ASTM Internationalstandard procedures to be used to perform the geomembraneleak location survey (see 2.1).5.2 A reali
35、stic test of the leak detection sensitivity should beperformed and documented as part of every leak locationsurvey. The leak detection sensitivity of the leak locationsystem via an actual or artificial leak is typically used accord-ing to the corresponding standard practices for the various leakloca
36、tion systems. The procedures for installing the actual leakholes for determining the leak detection sensitivity listed in thecorresponding ASTM procedure can be used with the modifi-cations described in 5.3 to place blind actual leaks.5.3 The various electrical leak location practices all specifythe
37、 use of actual leaks and procedures for making those actualleaks to determine the survey parameters and verify properD7909 142system operation. Leak detection is dependent upon the siteconditions at each leak. Site conditions that affect leak detec-tion sensitivity (particularly for surveys with ear
38、th materials onthe geomembrane, to some degree with surveys on baregeomembranes) include:5.3.1 Having adequate moisture throughout the overburdenmaterial and near subgrade,5.3.2 Moisture in the leak,5.3.3 The presence of dry insulating materials such asgeotextile or geonet in contact with the leak,5
39、.3.4 Contact of the geomembrane with the overburden andsubgrade,5.3.5 Degree of isolation of the overburden from earthground or the conducting material under the geomembrane,and5.3.6 The composition of the material in contact with theliner (large stones may bridge a leak).5.4 Because of these varyin
40、g site conditions, detecting aleak of the same size as the actual leak used to determine theleak detection sensitivity as specified in the ASTM Interna-tional standards (see 2.1) could be problematic. Better leakdetection sensitivity will be obtained at some locations, andworse leak detection sensit
41、ivity will be obtained at otherlocations. The specific guidelines for installing blind actualleaks are:5.4.1 The preferred blind actual leaks are to be constructedby drilling a hole with a minimum diameter of 1.0 mm forexposed geomembranes (1.4 mm for a blind actual leak for awater covered leak dete
42、ction survey and 6.4 mm for a blindactual leak for an earthen covered leak detection survey) that isto be tested at the time of geomembrane installation. The blindactual leaks shall be installed the same day as the geomem-brane installation, and as early as practical before the geomem-brane leak loc
43、ation survey is performed so that the blind testleak will be exposed to the same conditions of rainfall,condensation, consolidation, and equilibrium as the rest of thegeomembrane in the installation. If the blind actual leakscannot be installed the same day as during geomembraneplacement and install
44、ation, the diameters of the blind actualleak shall be increased to twice the above-mentioned diam-eters. Specifically, the blind actual leak diameter would resultinto using a diameter of 12.8 mm for geomembranes that are tobe covered with earth materials, 2.8 mm for geomembranesthat are to be covere
45、d with water, and 2.0 mm for baregeomembranes.5.4.2 For a double geomembrane system or underlyinggeosynthetic clay liner (GCL), procedures shall ensure that thedrill bit does not damage the secondary geomembrane or GCL.The hole shall be drilled, and the drill bit moved forward andbackward in the hol
46、e so the geomembrane material is removedrather than just displaced. (WarningBecause of the shock orelectrocution hazard that may be involved with high voltage,do not attempt to drill the blind actual leak with the excitationpower supply on or connected.)5.4.3 The blind actual leaks are to be install
47、ed by the owneror a representative of the owner without revealing the locationsto the leak location practitioner or others.5.4.4 The locations of the blind actual leaks shall bedocumented using appropriate land-surveying methods so theblind actual leaks can be located for future repair.5.4.5 The bli
48、nd actual leaks shall be put in representativelocations and not on wrinkles, areas of bridging, in fusionseams, or other areas where the geomembrane is not in contactwith the subgrade. They should not be placed within5moftheedge of the survey area.5.4.6 The blind actual leaks shall be backfilled wit
49、h acompaction representative of the rest of the installation. Ensurethat any cavity made by the drill in the subgrade under theblind actual leak is filled with soil.5.4.7 The number of placed blind actual leaks should beconsistent with the size and complexity of the overallinstallation, as well as with the purposes for which the blindactual leaks are installed. The owner or owners representativeshould consider the cost of installing, surveying, documenting,and repairing the blind actual leaks and the fact that a repairweld or patch of inferior integrity will replace an o
