1、Designation: D5921 96 (Reappproved 2010)Standard Practice forSubsurface Site Characterization of Test Pits for On-SiteSeptic Systems1This standard is issued under the fixed designation D5921; the number immediately following the designation indicates the year oforiginal adoption or, in the case of r
2、evision, 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.INTRODUCTIONMany State and local jurisdictions have requirements for evaluating sites for approval of on-site
3、septic systems. This practice provides a method to describe and interpret subsurface characteristics toevaluate sites for septic systems. All characteristics used in this practice influence the ability of a siteto provide treatment and disposal of septic tank effluent. However, this practice is not
4、meant to be aninflexible description of investigation requirements. State and local jurisdictions may require fewer orgreater numbers of subsurface features to evaluate a site.This practice primarily follows the U.S. Department of Agriculture, Soil Conservation Service(SCS) soil classification syste
5、m, which encompasses a systematic framework for soil morphologicalcharacterization. The SCS classification the most prevalent system in use for on-site septic systems.This practice can be complemented by application of other soil description techniques as appropriate,such as the Unified Soil Classif
6、ication System (D2485).1. Scope1.1 This practice covers procedures for the characterizationof subsurface soil conditions at a site as part of the process forevaluating suitability for an on-site septic system. This practiceprovides a method for determining the usable unsaturated soildepth for septic
7、 tank effluent to infiltrate for treatment anddisposal.1.2 This practice describes a procedure for classifying soilby field observable characteristics within the United StatesDepartment of Agriculture, Soil Conservation Service (SCS)classification system.2The SCS classification system is definedin R
8、efs (14),3not in this practice. This practice is based onvisual examination and manual tests that can be performed inthe field. This practice is intended to provide information aboutsoil characteristics in terms that are in common use by soilscientists, public health sanitarians, geologists, and eng
9、ineerscurrently involved in the evaluation of soil conditions for septicsystems.1.3 This procedure can be augmented by Test Method D422,when verification or comparison of field techniques is required.Other standard test methods that may be used to augment thispractice include: Test Methods D2325, D3
10、152, D5093, D3385,and D2434.1.4 This practice is not intended to replace Practice D2488which can be used in conjunction with this practice if construc-tion engineering interpretations of soil properties are required.1.5 This practice should be used in conjunction with D5879to determine a recommended
11、 field area for an on-site septicsystem. Where applicable regulations define loading rates-based soil characteristics, this practice, in conjunction withD5925, can be used to determine septic tank effluent applica-tion rates to the soil.1.6 This practice should be used to complement standardpractice
12、s developed at state and local levels to characterize soilfor on-site septic systems.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 does not purport to address all of thesafety concerns, if any, associated
13、 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.1.9 This practice offers a set of instructions for performingone or more specific operations. This documen
14、t cannot replaceeducation or experience and should be used in conjunction1This practice is under the jurisdiction of ASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.01 on Surface andSubsurface Characterization.Current edition approved May 1, 2010. Published Se
15、ptember 2010. Originallyapproved in 1996. Last previous edition approved in 2003 as D592196(2003)e1.DOI: 10.1520/D5921-96R10.2In 1995, the name of the SCS was changed to Natural Resource ConservationService. This guide uses SCS rather than NRCS because referenced documents werepublished before the n
16、ame change.3The boldface numbers given in parentheses refer to a list of references at theend of the text.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.with professional judgment. Nat all aspects of this practice maybe applicable i
17、n 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. The word “Standard” in thetitle of this
18、document means only that the document has beenapproved through the ASTM consensus process.2. Referenced Documents2.1 ASTM Standards:4D422 Test Method for Particle-Size Analysis of SoilsD653 Terminology Relating to Soil, Rock, and ContainedFluidsD2325 Test Method for Capillary-Moisture Relationshipsf
19、or Coarse- and Medium-Textured Soils by Porous-PlateApparatus5D2434 Test Method for Permeability of Granular Soils(Constant Head)D2488 Practice for Description and Identification of Soils(Visual-Manual Procedure)D3152 Test Method for Capillary-Moisture Relationshipsfor Fine-Textured Soils by Pressur
20、e-MembraneApparatus5D3385 Test Method for Infiltration Rate of Soils in FieldUsing Double-Ring InfiltrometerD5093 Test Method for Field Measurement of InfiltrationRate Using Double-Ring Infiltrometer with Sealed-InnerRingD5879 Practice for Surface Site Characterization for On-Site Septic SystemsD592
21、5 Practice for Preliminary Sizing and Delineation ofSoil Absorption Field Areas for On-Site Septic Systems53. Terminology3.1 Definitions:3.1.1 limiting depthfor the purpose of determining suit-ability for on-site septic systems, the depth at which the flow ofwater, air, or the downward growth of pla
22、nt roots is restricted.3.1.2 mottlespots or blotches of different colors or shadesof color interspersed with the dominant color (5).InSCS(3)practice mottles associated with wetness in the soil are calledredox concentrations or redox depletions.3.1.3 pocket penetrometera hand operated calibratedsprin
23、g instrument used to measure resistance of the soil tocompressive force.3.1.4 potentially suitable field areathe portions of a sitethat remain after observing limiting surface features such asexcessive slope, unsuitable landscape position, proximity towater supplies, and applicable setbacks have bee
24、n excluded.3.1.5 recommended field areathe portion of the poten-tially suitable field area at a site that has been determined to bemost suitable as a septic tank soil absorption field or filter bedbased on surface and subsurface observations.3.1.6 unsaturatedsoil water condition at which the voidspa
25、ces that are able to be filled are less than full.3.1.7 vertical separationthe depth of unsaturated, native,undisturbed soil between the bottom of the disposal componentof the septic system and the limiting depth.4. Summary of Practice4.1 This practice describes a field technique using visualexamina
26、tion and simple manual tests for characterizing andevaluating soils and identifying any limiting depth.5. Significance and Use5.1 This practice should be used as part of the evaluation ofa site for its potential to support an on-site septic system inconjunction with Practice D5879 and Practice D5925
27、.5.2 This practice should be used after applicable steps inPractice D5879 have been performed to document and identifypotentially suitable field areas.5.3 This practice should be used by those who are involvedwith the evaluation of properties for the use of on-site septicsystems. They may be require
28、d to be licensed, certified, meetminimum educational requirements by the area governingagencies, or all of these.5.4 This practice requires exposing the soil to an appropriatedepth (typically 1.5 to 1.8 m, or greater as site conditions orproject objectives require) for examining the soil morphologic
29、characteristics related to the performance of on-site septicsystems.6. Limitations6.1 The water content of the soil will affect its properties.The soil should be evaluated in the moist condition because thenormal operating state of the septic system is a moist condition.If the soil is dry, moisten i
30、t.6.2 This practice is not applicable to frozen soil.6.3 Optimum lighting conditions for determining soil colorare full sunlight from mid-morning to mid-afternoon. Lessfavorable lighting conditions exist when sun is low or skies arecloudy or smoky. If artificial light is used, it should be as nearth
31、e light of mid-day as possible.7. Apparatus7.1 Tools typically used are a soil knife or a flat blade screwdriver, tape measure, pencil and paper, Munsell soil colorcharts (6), water bottle, wash rag, and a sack to carry samplesif required. A pocket penetrometer may also be useful. Whenthe presence o
32、f carbonate may be significant in soils, dilutehydrochloric acid (10 % HCl) should be used.7.2 A backhoe will facilitate excavation of the test pits forexamination. However, if the site is inaccessible or funds arelimited, one may excavate by hand with a shovel. Dependingon site conditions, power dr
33、iven or hand held soil augers mayalso be suitable. Tube samplers allow description of soilmorphologic features providing the size of the feature does notexceed the diameter of the core. Augers generally destroy suchmorphologic features as soil structure and porosity. The advan-tage of augers and tub
34、e samplers is that they are generally4For referenced 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.5Withdrawn. The last app
35、roved version of this historical standard is referencedon www.astm.org.D5921 96 (Reappproved 2010)2faster and less expensive than excavated pits. Their disadvan-tage is that they sample a smaller area of soil, preventingcharacterization of lateral changes in horizon boundaries anddescription of larg
36、er-scale morphologic features. Use of probesor augers as an alternative to excavated pits requires a higherdegree of experience and knowledge about soils in an area.7.3 For preliminary examination of a site, one may probevertically into the soil to get a feel for the presence and depthto a compacted
37、 layer, or a water table. Tools that might be usedinclude a digging bar, tile probe, post hole digger, or hand soilauger.8. Location of Sampling Points8.1 Test pits or other subsurface sampling points should belocated in the potentially suitable field area as determined usingPractice D5879, taking i
38、nto consideration proximity of sourceof waste water and down slope of source, if possible. Locatingdown slope gives most flexibility in system design by allowingeither gravity flow or pressure distribution. A preliminarysizing of the field should be performed in accordance withPractice D5925 to dete
39、rmine placement of the sample points.Generally, sample points should be located on diagonal cornersof the preliminary drainfield area so as to avoid disturbing thesoil within the recommended field area. Depending on siteconditions, additional sample points may be required to iden-tify a recommended
40、field area.9. Procedure9.1 Orient the excavation to expose the vertical face to thebest light.9.2 Excavate the test pit to a depth sufficient to satisfy thevertical separation required by the governing agency. If thelimiting depth is too shallow to meet the vertical separationrequirement, it may be
41、desirable to excavate deeper to deter-mine if the layer is underlain by permeable material.9.3 Enter the test pit using all applicable safety requirementsand examine the soil layers, or horizons. Select a representativearea to examine in detail.69.4 Using a soil knife or other tool, expose the natur
42、al soilstructure in an area approximately 0.5 m in width the fullheight of the test pit.9.5 Describe master soil horizons following the criteria inTable 1. Horizons are separated by boundaries. Locate theseboundaries by changes in color, texture, or structure.9.6 For each layer describe and test as
43、follows:9.6.1 Measure the depth of the layer from the soil-airinterface. Positive numerical values indicate increasing depth.9.6.2 Describe color of soil with soil in the moist state. UseMunsell color chart (6) designation for hue, value, and chroma.Include the color name. Indicate lighting conditio
44、ns, if otherthan direct sunlight.9.6.3 Estimate the volumetric percentage of rock fragments(see Fig. 1).9.6.4 Describe size, shape, and percentage of rock frag-ments (see Table 2).9.6.5 Describe the texture of the8).10.2.3 Horizons with iron and manganese concretions mayindicate seasonal saturation
45、or capillary fringe. Depth to ironand manganese concentrations will generally provide the mostconservative estimate to depth to seasonal high water table.10.2.4 Where the capillary fringe is also considered as partof the saturated zone for defining the limiting depth, soiltexture can be used to esti
46、mate the thickness of the capillaryfringe as shown in Table 12.10.3 Depth to Impermeable LayersObservable soil fea-tures that indicate layers that limit downward movement ofwater include slowly permeable soil genetic horizons, such asfragipans, duripans, and caliche, soil horizons with very weak,pla
47、ty or massive structure, very firm or very hard ruptureresistance, layers that are moderately cemented, strongly ce-mented or indurated, and high penetration resistance.10.4 Depth to Excessively Permeable LayersCoarse sand,very gravelly, extremely gravelly or soils with greater than15 % rock fragmen
48、ts larger than gravel generally do notprovide adequate treatment of wastewater effluent. Such layersare identified based on the size class and amount of sand in the2 mm fraction.10.5 Strong textural contrasts between soil layers (fine-grained over coarse grained, or coarse-grained over fine-grained)
49、 impede both unsaturated and saturated flow. Whereexcess soil water percolates through the soil, such contrastswill also be indicated by mottling, whereas mottling may notbe evident in areas where evapotranspiration exceeds precipi-tation.11. Report11.1 Reporting of results of the subsurface investigationshould be integrated with the results of the surface investiga-tion. The local or state regulatory authority may have devel-oped forms or formulas for investigation reports, in which case,these should be used.11.2 The report on the results of the subsurface soilsexaminatio
