1、Designation: D 5921 96 (Reappproved 2003)e1Standard Practice forSubsurface Site Characterization of Test Pits for On-SiteSeptic Systems1This standard is issued under the fixed designation D 5921; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、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.e1NOTEReferences 1 and 4 were updated editorially in November 2003.INTRODUCTIONMany State and local juri
3、sdictions have requirements for evaluating sites for approval of on-siteseptic 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 treatm
4、ent and disposal of septic tank effluent. However, this practice is not 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
5、of Agriculture, Soil Conservation Service(SCS) soil classification system, 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 soi
6、l description techniques as appropriate,such as the Unified Soil Classification System (D 2485).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 practiceprov
7、ides a method for determining the usable unsaturated soildepth for septic 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
8、 (SCS)classification system.2The SCS classification system is definedin Refs (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 com
9、mon use by soilscientists, public health sanitarians, geologists, and engineerscurrently involved in the evaluation of soil conditions for septicsystems.1.3 This procedure can be augmented by Test MethodD 422, when verification or comparison of field techniques isrequired. Other standard test method
10、s that may be used toaugment this practice include: Test Methods D 2325, D 3152,D 5093, D 3385, and D 2434.1.4 This practice is not intended to replace Practice D 2488which can be used in conjunction with this practice if construc-tion engineering interpretations of soil properties are required.1.5
11、This practice should be used in conjunction with D5879to determine a recommended 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 r
12、ates to the soil.1.6 This practice should be used to complement standardpractices 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 as thestandard.1.8 This standard does not purport to address all of thesafety conc
13、erns, 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.1.9 This practice offers a set of instructions for performingone or more specific
14、operations. This document 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 F
15、eb. 10, 1996. Published November 1996.2In 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 name change.3The boldface numbers given in parentheses refer to a list of references at
16、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 in all circumstances. This ASTM standard is notintended to represent or replace the stan
17、dard 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 document means only that the document has beenapproved through the ASTM consensus proce
18、ss.2. Referenced Documents2.1 ASTM Standards:4D 422 Standard Test Method for Particle-Size Analysis ofSoilsD 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 2325 Test Method for Capillary-Moisture Relationshipsfor Coarse- and Medium-Textured Soils by Porous-PlateApparatusD 2434 Test Met
19、hod for Permeability of Granular Soils(Constant Head)D 2488 Practice for Description and Identification of Soils(Visual-Manual Procedure)D 3152 Test Method for Capillary-Moisture Relationshipsfor Fine-Textured Soils by Pressure-Membrane ApparatusD 3385 Test Method for Infiltration Rate of Soils in F
20、ieldUsing Double-Ring InfiltrometerD 5093 Test Method for Field Measurement of InfiltrationRate Using a Double-Ring Infiltrometer with a Sealed-Inner RingD 5879 Practice for Surface Site Characterization for On-Site Septic SystemsD 5925 Practice for Preliminary Sizing and Delineation ofSoil Absorpti
21、on Field Areas for On-Site Septic Systems3. 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 plant roots is restricted.3.1.2 mottlespots or blotches of different
22、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 calibratedspring instrument used to measure resistance of the soil tocompressive
23、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 been excluded.3.1.5 recommended field areathe portion of the poten-ti
24、ally 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 voidspaces that are able to be filled are less than full.3.1.7 vertical s
25、eparationthe 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 visualexamination and simple manual tests for characterizing andevaluating soil
26、s 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 D 5879 and Practice D 5925.5.2 This practice should be used after applicable steps inPract
27、ice D 5879 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 required to be licensed, certified, meetminimum educational requiremen
28、ts 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 morphologiccharacteristics related to the performance of on-site septicsys
29、tems.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 it.6.2 This practice is not applicable to frozen soil.6.3 Optimu
30、m 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 nearthe light of mid-day as possible.7. Apparatus7.1 Tools typically
31、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 of carbonate may be significant in soils, dilutehydrochloric aci
32、d (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 driven or hand held soil augers mayalso be suitable. Tube sampler
33、s 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 tube samplers is that they are generallyfaster and less expensive
34、than excavated pits. Their disadvan-tage is that they sample a smaller area of soil, preventing4For 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 Documen
35、t Summary page onthe ASTM website.D 5921 96 (Reappproved 2003)e12characterization of lateral changes in horizon boundaries anddescription of larger-scale morphologic features. Use of probesor augers as an alternative to excavated pits requires a higherdegree of experience and knowledge about soils i
36、n 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 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
37、Test pits or other subsurface sampling points should belocated in the potentially suitable field area as determined usingPractice D 5879, taking into consideration proximity of sourceof waste water and down slope of source, if possible. Locatingdown slope gives most flexibility in system design by a
38、llowingeither gravity flow or pressure distribution. A preliminarysizing of the field should be performed in accordance withPractice D 5925 to determine placement of the sample points.Generally, sample points should be located on diagonal cornersof the preliminary drainfield area so as to avoid dist
39、urbing thesoil within the recommended field area. Depending on siteconditions, additional sample points may be required to iden-tify a recommended 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
40、thevertical separation required by the governing agency. If thelimiting depth is too shallow to meet the vertical separationrequirement, it may be 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 requirement
41、sand examine the soil layers, or horizons. Select a representativearea to examine in detail.59.4 Using a soil knife or other tool, expose the natural 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
42、1. Horizons are separated by boundaries. Locate theseboundaries by changes in color, texture, or structure.9.6 For each layer describe and test as 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
43、 with soil in the moist state. UseMunsell color chart (6) designation for hue, value, and chroma.Include the color name. Indicate lighting conditions, 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 roc
44、k 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 or capillary fringe. Depth to ironand manganese concentrations will generally provide the mostconservative estimate to depth to seasonal high water table
45、.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 estimate the thickness of the capillaryfringe as shown in Table 13.10.3 Depth to Impermeable LayersObservable soil fea-tures that indicate layers that limit
46、downward movement ofwater include slowly permeable soil genetic horizons, such asfragipans, duripans, and caliche, soil horizons with very weak,platy or massive structure, very firm or very hard ruptureresistance, layers that are moderately cemented, strongly ce-mented or indurated, and high penetra
47、tion resistance.10.4 Depth to Excessively Permeable LayersCoarse sand,very gravelly, extremely gravelly or soils with greater than15 % rock fragments larger than gravel generally do notprovide adequate treatment of wastewater effluent. Such layersare identified based on the size class and amount of
48、sand in the2 mm fraction.10.5 Strong textural contrasts between soil layers (fine-grained over coarse grained, or coarse-grained over fine-grained) impede both unsaturated and saturated flow. Whereexcess soil water percolates through the soil, such contrastswill also be indicated by mottling, wherea
49、s 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 soilsexamination should include the following:11.2.1 Site map prepared for the surface site characteriza-tion investigation (see D5879) with locations of the test pits o
