ASTM D5925-96e1
(Practice)Standard Practice for Preliminary Sizing and Delineation of Soil Absorption Field Areas for On-Site Septic Systems (Withdrawn 2005)
Standard Practice for Preliminary Sizing and Delineation of Soil Absorption Field Areas for On-Site Septic Systems (Withdrawn 2005)
SCOPE
1.1 This practice covers procedures for estimating the dimensions and marking the boundaries of a soil absorption area for an on-site septic system involving residential-strength wastewater. It can also be used to estimate the dimensions of commercial on-site septic systems where wastewater strengths are similar to residential wastewater.
1.2 This practice can also be used for marking the boundaries of the area for a septic system construction filter bed.
1.3 This practice can be used at any site where a potentially suitable or recommended field area has been identified in accordance with Practices D 5879 and D 5921.
1.4 Non-metric units remain the common practice in design and installation of on-site waste disposal systems, and are used in this practice. Use of SI units given in parentheses is encouraged, if acceptable to the appropriate permitting agency.
1.5 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.
WITHDRAWN RATIONALE
This practice covers procedures for estimating the dimensions and marking the boundaries of a soil absorption area for an on-site septic system involving residential-strength wastewater.
Formerly under the jurisdiction of Committee D18 on Soil and Rock, this practice was withdrawn in May 2005 in accordance with section 10.5.3.1 of the Regulations Governing ASTM Technical Committees, which requires that standards shall be updated by the end of the eighth year since the last approval date.
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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e1
Designation:D5925–96
Standard Practice for
Preliminary Sizing and Delineation of Soil Absorption Field
Areas for On-Site Septic Systems
This standard is issued under the fixed designation D 5925; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Paragraph 1.6 was added editorially October 1998.
1. Scope 2. Referenced Documents
1.1 This practice covers procedures for estimating the di- 2.1 ASTM Standards:
mensions and marking the boundaries of a soil absorption area D 5879 Practice for Surface Site Characterization for On-
for an on-site septic system involving residential-strength Site Septic Systems
wastewater. It can also be used to estimate the dimensions of D 5921 PracticeforSubsurfaceCharacterizationofTestPits
commercial on-site septic systems where wastewater strengths for On-Site Septic Systems
are similar to residential wastewater.
3. Terminology
1.2 This practice can also be used for marking the bound-
3.1 Definitions of Terms Specific to This Standard:
aries of the area for a septic system constructed filter bed.
1.3 This practice can be used at any site where a potentially 3.1.1 clinometer—an instrument for measuring inclination,
as in topographic slope.
suitable or recommended field area has been identified in
accordance with Practices D 5879 and D 5921. 3.1.2 constructed filter bed (CFB)—for the purposes of this
practice, material, usually of a sandy texture, placed above or
1.4 Non-metric units remain the common practice in design
and installation of on-site waste disposal systems, and are used in an excavated portion of the natural soil for filtration and
purification of wastewater from an on-site septic system.
in this practice. Use of SI units given in parentheses is
encouraged, if acceptable to the appropriate permitting agency. 3.1.3 on-site septic system—for the purposes of this prac-
tice, any wastewater treatment and disposal system that uses a
1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the septic tank or functionally equivalent device for collecting
responsibility of the user of this standard to establish appro- waste solids and treats wastewater using natural soils, or
constructed filter beds with disposal of the treated wastewater
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. into the natural soil.
3.1.4 potentially suitable field area—the portions of a site
1.6 This practice offers a set of instructions for performing
one or more specific operations. This document cannot replace that remain after observable limiting surface features, such as
excessive slope, unsuitable landscape position, proximity to
education or experience and should be used in conjunction
withprofessionaljudgment.Notallaspectsofthispracticemay water supplies, and applicable setbacks, have been excluded.
3.1.5 recommended field area—the portion of the poten-
be applicable in all circumstances. This ASTM standard is not
intended to represent or replace the standard of care by which tially suitable field area at a site that has been determined to be
most suitable for an on-site septic system soil absorption field
the adequacy of a given professional service must be judged,
nor should this document be applied without consideration of or filter bed based on surface and subsurface observations.
3.1.6 soil absorption (SA) area—an area of natural soil used
a project’s many unique aspects. The word “Standard” in the
title of this document means only that the document has been for filtration and purification of wastewater from an on-site
septic system.
approved through the ASTM consensus process.
3.1.7 soil absorption field area (SAF)—anareathatincludes
soil absorption trenches and any soil barriers between the
trenches. Also called a leachfield.
This practice is under the jurisdiction of ASTM Committee D18 on Soil and
Rockand is the direct responsibility of Subcommittee D18.01 on Surface and
Subsurface Characterization.
Current edition approved April 10, 1996. Published November 1996. Annual Book of ASTM Standards, Vol 04.09.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D5925
3.1.8 soil absorption trench—an excavated trench, usually 6. Procedure for Estimating Field Dimensions
1.5 to 3 ft wide that receives wastewater for treatment. Also
6.1 Use this procedure for preliminary sizing of the area
called a lateral or leachline.
required for a soil absorption field or constructed filter bed for
the purpose of staking a field areas as described in Section 7.
4. Significance and Use
This procedure should also be used whenever marginal site
4.1 This practice should be used in conjunction with a
surface and subsurface conditions indicate doubt as to whether
surface and subsurface site investigation to delineate a recom-
there is a large enough area that is suitable for an on-site septic
mended field area that is adequate for any septic system that
system.
can reasonably be anticipated for the site. If actual design
6.2 Factors that affect the soil absorption field (SAF) area
results in a smaller field area, the boundaries can be modified
requirements include wastewater quantity (typically expressed
accordingly.
as gallons per day (gpd), loading rate (typically expressed as
4.2 Staking and flagging procedures in the practice help
gpd/ft ) that is derived from soil characteristics or percolation
prevent accidental disturbance of a recommended septic sys-
test results (see 6.3.3), and trench spacing, that determines the
tem field area by equipment traffic and other construction 3
area of soil between absorption trenches. Dividing Factor 1 by
activities prior to installation of the system. Soil disturbance 4
Factor2givesthetotalrequiredsoilabsorption(SA)area. The
resulting in compaction from heavy equipment traffic or
SA area plus the area represented by soil barriers between
removal by excavation equipment usually invalidates the
trenches yields the SAF area. In some jurisdictions the SAarea
results of the surface and subsurface investigation that led to
may be determined by the number of bedrooms based on
recommendation of a field area.
assumptions concerning wastewater flow and loading rates.
4.3 In the event of suspected disturbance or removal of
Factors affecting the area required for constructed filter beds
natural soil in the recommended field area, soil elevation
are the same as for soil absorption fields.
benchmarks established by this practice allow assessment of
6.3 Method for Estimating Soil Absorption Field
the actual extent of disturbance or soil removal.
Dimensions—The method described here assumes residential-
4.4 This practice should also be used where topographic
strength wastewater and includes tables that should be gener-
limitations create uncertainty as to whether a potentially
ally applicable to most parts of the United States. Alternative
suitable field area for a septic system will provide a large
tables using other wastewater flow and soil loading rates can
enough absorption area to treat anticipated wastewater flows.
easily be developed. The method for estimating a SAF area
In such situations clear demarcation of the suitable areas will
involves the following steps: determining wastewater flow,
also provide greater assurance of proper system installation.
determining soil loading rate, determining required SA area,
determining the number of trenches and their length to provide
5. Field Equipment
the required SA area, and determining the width of the field
5.1 A clinometer or hand level and rod that is marked in
based on the number of trenches.
feet/metric increments and at the eye level of the investigator
6.3.1 Wastewater Flow—Typically wastewater flow is de-
are used for measuring slope and delineating topographic
termined by the number of bedrooms in a residence. 150 gpd
contours.Acompass may be useful for defining position of the
per bedroom, recommended by U.S. EPA (1), is widely used.
fieldarea.Asinglepersoncantakemeasurementsiftherodhas
Table 1 includes rates of 150, 300, 450, and 600 gpd that
a point that can be driven into the ground so that it stands
correspond to a 1-, 2-, 3-, and 4-bedroom house, respectively.
vertically, as described in 7.1. An extendible surveyor’s rod
with a tripod can also be used by a single person and may
facilitate the elevation benchmarking procedure described in
7.2. Other factors that may need to be considered include: wastewater strength
(suspended solids, biological/chemical oxygen demand, nitrogen, phosphorus, etc.),
5.2 A100fttapeorlongercanbeusedtomeasurethelength
potential for ground-water mounding under absorption trenches or constructed filter
andwidthofthefieldarea.Ascrewdriverorspikeisalsouseful
beds, and evapotranspiration. Standard loading rates based on soil characteristics or
for anchoring one end of the tape when making measurements.
percolation test results usually assume residential-strength wastewater. Wastewaters
with parameters that differ significantly from residential wastewater require special
Where there are no concerns about the adequacy of the
design procedures that are not addressed in this practice. Section 6.3.5 discusses
available suitable area, pacing can be used as an alternative to
situations where ground-water mounding analysis may need to be considered. In
a tape. In this case, the investigator should periodically check
temperate climates evapotranspiration is usually not considered when determining
the accuracy of his or her pace against a known distance. the required SA area because it is zero during winter months. In areas where
evapotranspiration is significant throughout the year, it may be possible to reduce
5.3 Stakes and flagging are used to mark the corners and
SA area requirements. This requires a water budget analysis for the time of year
otherboundariesofthefieldarea.Stakescanbeofanymaterial
when evapotranspiration is at a minimum and adjusting the field size accordingly.
(wood, fiberglass, metal) that is durable enough to remain
For example, if 20 % of the wastewater entering the soil could be expected to be
transpired, the field size could be reduced by one-fifth.
standing during the period from staking until installation of the
This actually gives only the absorption area of the bottom of the trench.
system. If the area is to be mowed, the stakes should be tall
Depending on the depth of effluent in a trench additional absorption area is provided
enough and sturdy enough to prevent accidental damage to the
by the sidewalls. Normal practice is to ignore this area when calculating required
stake or the mower. If there is any possibility that the stakes
soil absorption area. However, some jurisdictions allow credit for sidewall area.
This method can also be used to estimate field dimensions for grade soil
might be confused with other markers at the site, colored
absorption fields, and trench systems where the lower portions are filled with filter
flagging coded for different purposes can be used. Generally,
bed material.
actual fencing is not required unless heavy equipment traffic is
The boldface numbers given in parentheses refer to a list of references at the
expected to run regularly by the area. end of the text.
D5925
TABLE 1 Soil Absorption/Filter Bed Area Requirements for
Different Wastewater Flow and Soil Loading Rates
Wastewater Flow
Soil Loading, R
600 gal/
150 gal/day 300 gal/day 450 gal/day
day
Soil Absorption Area
ft
gal/day Square Square Square Square
2 2 2 2
gal/day
ft ft ft ft
ft Root Root Root Root
0.2 5.0 750 . 1500 . 2250 . 3000 .
0.25 4.0 600 . 1200 . 1800 . 2400 .
0.3 3.3 500 . 1000 . 1500 . 2000 .
0.35 2.9 429 . 857 . 1286 . 1714 .
0.4 2.5 375 . 750 . 1125 . 1500 .
0.45 2.2 333 . 667 . 1000 . 1333 .
0.5 2.0 300 . 600 . 900 . 1200 .
0.6 1.7 250 16 500 22 750 27 1000 32
0.7 1.4 214 15 429 21 643 25 857 29
0.8 1.3 188 14 375 19 563 24 750 27
0.9 1.1 167 13 333 18 500 22 667 26
1.0 1.0 150 12 300 17 450 21 600 24
1.1 0.9 136 12 273 17 409 20 545 23
1.2 0.8 125 11 250 16 375 19 500 22
Some jurisdictions may use different loading rates (120 to 200
gpd per bedroom, 60 to 150 gpd per person). Reference (2)
compiles design flow rates specified in state regulations in the
United States.
6.3.2 Soil Loading Rate—Increasingly,septicsystemdesign
is being based on soil loading rates based on soil texture and
structure as determined by subsurface site characterization as
covered in Practice D 5879. Table 1 includes loading rates
FIG. 1 EPA’s and Winneberger’s Recommendations for
from 0.2 to 1.2 gpd/ft . Loading rates may also be determined
Absorptions Area (Square Feet per Gallon of Sewage per Day)
by percolation test results (3). Fig. 1 can be used to convert
Versus Measured Percolation (Minutes per Inch) (5)
percolation rates measured as minutes per inch (mpi) to
recommended SAarea loading rates as suggested by U.S. EPA
(7) and Winneberger (4). If percolation test results are reported ft , and the trenches are 3 ft wide, there are three possible
in inches/hour, convert to minutes per inch (mpi = 60/in./h). configurations: (1) two trenches 100 ft long, (2) three trenches
Soil loading rates are lower than the saturated hydraulic 70 ft long (that provide a little more than the required area),
conductivity of soil in order to take into account reduced and (3) four trenches 50 ft long. Select the configuration that
infiltrationresultingfromdevelopmentofabiologicalclogging best fits the site, giving preferences for the configuration that
mat on absorption trench surfaces and to allow for unsaturated minimizes the number of trenches. This determines the length
flow. Some jurisdictions may require consideration of climatic of the field for staking, as described in Section 7. Where the
factors such as precipitation and evapotranspiration when vertical separation between the bottom of the disposal compo-
determining soil loading rates for soil. Reference (2) compiles nent of the on-site septic system and a limiting layer is at or
application rates defined in state regulations in the United near the minimum allowed, ground-water mounding calcula-
States. tions may be required, especially if more than two or three
6.3.3 Soil Absorption Area—Table 1 shows soil absorption
trenches are required.
areas required for commonly used wastewater flows and soil 6.3.6 Width of Fiel
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