ASTM D5921 - 96(2010)

    Standard Practice for Subsurface Site Characterization of Test Pits for On-Site Septic Systems

    Active Standard ASTM D5921 | Developed by Subcommittee: D18.01

    Book of Standards Volume: 04.09


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    ASTM D5921

    Significance and Use

    This practice should be used as part of the evaluation of a site for its potential to support an on-site septic system in conjunction with Practice D5879 and Practice D5925.

    This practice should be used after applicable steps in Practice D5879 have been performed to document and identify potentially suitable field areas.

    This practice should be used by those who are involved with the evaluation of properties for the use of on-site septic systems. They may be required to be licensed, certified, meet minimum educational requirements by the area governing agencies, or all of these.

    This practice requires exposing the soil to an appropriate depth (typically 1.5 to 1.8 m, or greater as site conditions or project objectives require) for examining the soil morphologic characteristics related to the performance of on-site septic systems.

    1. Scope

    1.1 This practice covers procedures for the characterization of subsurface soil conditions at a site as part of the process for evaluating suitability for an on-site septic system. This practice provides a method for determining the usable unsaturated soil depth for septic tank effluent to infiltrate for treatment and disposal.

    1.2 This practice describes a procedure for classifying soil by field observable characteristics within the United States Department of Agriculture, Soil Conservation Service (SCS) classification system. The SCS classification system is defined in Refs (14), not in this practice. This practice is based on visual examination and manual tests that can be performed in the field. This practice is intended to provide information about soil characteristics in terms that are in common use by soil scientists, public health sanitarians, geologists, and engineers currently involved in the evaluation of soil conditions for septic systems.

    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 this practice include: Test Methods D2325, D3152, D5093, D3385, and D2434.

    1.4 This practice is not intended to replace Practice D2488 which can be used in conjunction with this practice if construction engineering interpretations of soil properties are required.

    1.5 This practice should be used in conjunction with D5879 to determine a recommended field area for an on-site septic system. Where applicable regulations define loading rates-based soil characteristics, this practice, in conjunction with D5925, can be used to determine septic tank effluent application rates to the soil.

    1.6 This practice should be used to complement standard practices developed at state and local levels to characterize soil for on-site septic systems.

    1.7 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

    1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

    1.9 This practice offers a set of instructions for performing one or more specific operations. This document cannot replace education or experience and should be used in conjunction with professional judgment. Nat all aspects of this practice may be applicable in all circumstances. This ASTM standard is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied without consideration of a project's many unique aspects. The word Standard in the title of this document means only that the document has been approved through the ASTM consensus process.


    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    D422 Test Method for Particle-Size Analysis of Soils

    D653 Terminology Relating to Soil, Rock, and Contained Fluids

    D2325 Test Method for Capillary-Moisture Relationships for Coarse- and Medium-Textured Soils by Porous-Plate Apparatus

    D2434 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 Relationships for Fine-Textured Soils by Pressure-Membrane Apparatus

    D3385 Test Method for Infiltration Rate of Soils in Field Using Double-Ring Infiltrometer

    D5093 Test Method for Field Measurement of Infiltration Rate Using Double-Ring Infiltrometer with Sealed-Inner Ring

    D5879 Practice for Surface Site Characterization for On-Site Septic Systems

    D5925 Practice for Preliminary Sizing and Delineation of Soil Absorption Field Areas for On-Site Septic Systems


    ICS Code

    ICS Number Code 13.060.30 (Sewage water)

    UNSPSC Code

    UNSPSC Code


    DOI: 10.1520/D5921-96R10

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