[Federal Register Volume 63, Number 208 (Wednesday, October 28, 1998)]
[Notices]
[Pages 57651-57656]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-28467]


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DEPARTMENT OF AGRICULTURE

Natural Resources Conservation Service


Mining Specifications for Prime Farmland

AGENCY: Natural Resources Conservation Service, USDA.

ACTION: Notice of proposed specifications with request for comments.

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SUMMARY: The Natural Resources Conservation Service (NRCS) of the 
Department of Agriculture (USDA) is issuing proposed specifications for 
soil handling in relation to mining activities on prime farmland, as 
provided for in the Surface Mining Control and Reclamation Act of 1977 
(SMCRA). SMCRA requires the Secretary of Agriculture to establish 
specifications for the removal, storage, replacement, and 
reconstruction of prime farmland soils. The Soil Conservation Service, 
now called the Natural Resources Conservation Service, first proposed 
these specifications on February 19, 1988 (53 FR 4989). NRCS has made 
revisions to the proposed specifications and now seeks additional 
public comment prior to issuance of final specifications.

DATES: Comments must be received by November 27, 1998.

ADDRESSES: Mail written comments to Gary Nordstrom, Director, 
Conservation Operations Division, Natural Resources Conservation 
Service, P.O. Box 2890, Washington, D.C. 20013. Submit electronic 
comments to [email protected]

FOR FURTHER INFORMATION CONTACT: Gary Nordstrom, Director, Conservation 
Operations Division, Natural Resources Conservation Service, 202-720-
1845.

SUPPLEMENTARY INFORMATION: 

General Background on Proposed Specifications

    Section 515(b)(7) of the Surface Mining Control and Reclamation Act 
of 1977 (SMCRA), Public Law 95-87, 30 U.S.C., 1265(b)(7), authorizes 
the Secretary of Agriculture to establish specifications for soil 
removal, storage, replacement, and reconstruction for all prime 
farmlands, as identified in Section 507(b)(16) of the Act, 30 U.S.C. 
1257(b)(16), to be mined and reclaimed. This authority is delegated to 
NRCS in 7 CFR 2.61(a)(22).
    NRCS determined that national specifications for soil handling must 
allow for consideration of the wide diversity of soils, geology, 
climate, mining equipment, and crops in coal mining areas across the 
nation. These differences are recognized in the permanent program 
regulations published by the Office of Surface Mining Reclamation and 
Enforcement, U.S. Department of the Interior, specifically in 30 CFR 
823.4(a), which states that ``NRCS within each State shall establish 
specifications for prime farmland soil removal, storage, replacement, 
and reconstruction.''
    Accordingly, NRCS developed the specifications set forth in this 
proposed notice to ensure that local and site-specific factors are 
considered. Within the individual States, each NRCS State 
Conservationist will maintain and make available a local version of 
these specifications that incorporates the general criteria set forth 
in these specifications and any modifications made for the respective 
State. To the fullest extent possible, the basic specifications and the 
applicable modifications for individual States reflect the latest 
scientific information and experience regarding reclamation techniques.
    During the development of the proposed specifications, NRCS 
national office provided certain general guidelines to assist the NRCS 
State staffs in developing specifications at the local level. These 
guidelines were set out in the advance notice of the proposed rule 
published on August 26, 1985 (50 FR 34490). The first version of these 
proposed specifications was published on February 19, 1988 (53 FR 
4989). The specifications in this notice reflect comments received as a 
result of the 1988 publication and includes technical revisions based 
on research results and improvements in technology which have occurred 
since the 1988 publication.
    Although NRCS had originally intended to publish these 
specifications as a codified regulation under 7 CFR part 652, it has 
been determined that the guidance included within this notice is 
advisory in nature, not regulatory. Therefore, these specifications 
will not appear in the Code of Federal Regulations as a rule.

Discussion of the Proposed Specifications

    The Soil Removal section provides guidance on the identification of 
prime farmland soils where a published survey is not available and 
outlines how a soil scientist should proceed with identifying and 
sampling the soils to be removed for later replacement and 
reconstruction. This section identifies needed documentation of field 
conditions, including rooting zones; surface relief; pre-mining 
drainage conditions (including subsurface); flood frequency; physical, 
chemical, and morphological soil properties of the soils to be removed; 
and the equipment and procedures to be used in soil removal. The soil 
removal specifications address the handling of the various soil 
horizons encountered on prime farmland and the procedures to be 
followed if substitute materials are to be used. NRCS recognizes that 
compaction of prime farmland soils during removal and reconstruction is 
a significant factor in prime farmland reclamation and, therefore, the 
specifications include guidance to avoid compaction problems.
    In the Soil Stockpiling section, NRCS recognizes that stockpiling 
of soil horizons, while not the preferred procedure for reclamation, is 
often necessary because of weather conditions, limitations or 
availability of equipment, or the reclamation method utilized. These 
specifications provide guidance to ensure that if stockpiling is 
utilized, the soil resources will be protected until reconstruction 
begins. This section provides criteria for stockpile site selection, 
protection against contamination and loss, and temporary distribution 
if long-term stockpiling is required.
    In the Soil Reconstruction section, NRCS incorporates the principle 
of SMCRA that the reclamation of prime farmland requires the re-
establishment of the pre-mining productivity of the disturbed soils. 
The soil reconstruction specifications provide a framework which, if 
followed and the required conditions are achieved, should maximize the 
probability that the reconstructed soil will achieve the required 
productivity.
    Many factors contribute to the pre-mining productivity of prime 
farmland, including the chemical and physical characteristics of the 
soil horizons, the soil depth, the soil slope, and the

[[Page 57652]]

drainage conditions. Research has shown that when the post-mining soil 
characteristics are similar to the pre-mining characteristics, pre-
mining productivity can be achieved.
    These specifications provide for documentation of the 
characteristics of original soil, as required by sections 507 and 508 
of SMCRA, 30 U.S.C 1257 and 1258, and provide that the reconstructed 
soils should achieve, as best as possible, these characteristics. These 
specifications provide guidance on how to utilize pre-mining 
information in the development of a reconstruction plan for successful 
reclamation. This guidance includes provisions regarding rooting 
depths, chemical and physical characteristics of the soil horizons, and 
site conditions. These specifications also include erosion control 
measures to ensure that the reconstructed soils remain in place after 
reclamation.
    NRCS has attached appendices A and B for information and compliance 
assistance purposes. These appendices do not establish an obligation 
not otherwise imposed by rules and regulations, nor do they detract 
from obligations imposed by other rules and regulations. Appendix A 
contains information describing the procedures for determining the 
rooting zone of the pre-mined prime farmland soil. Appendix B contains 
information describing the procedure and quantitative specifications 
which can be used to evaluate the rooting zone of the reconstructed 
soil in relation to the pre-mined soil.

Implementation Issues

    It is important that the implementation and administration of the 
specifications be understood by everyone with an interest in the 
successful reclamation of surface mined prime farmlands. Once these 
specifications are finalized, NRCS will place these specifications in 
each NRCS State Office. NRCS will send copies to each State Regulatory 
Authority (RA) and each OSM office so that the specifications can be 
used in carrying out their responsibilities for prime farmland 
reclamation.
    The applicant for a mining permit on prime farmland will prepare a 
reclamation plan, as required by sections 507 and 508 of SMCRA, 30 
U.S.C. 1257 and 1258, based upon the particular prime farmland soils 
proposed to be mined, the equipment to be used, and the physical 
characteristics of the site. Because these conditions vary considerably 
among sites, the mining and reclamation plans will also vary. The RA 
must rely on its technical staff to assure the proposed reclamation 
plan will likely yield the required results. The RA technical staff 
will utilize the NRCS specifications in making their recommendations 
for approving, disapproving, or revising the proposed reclamation plan. 
In addition to the plan review by the RA technical staff, the RA will 
consult with the NRCS State Conservationist on the plan prior to a 
final decision. The NRCS State Conservationist will review and comment 
on the proposed reclamation plan and, if the plan does not reflect NRCS 
specifications, the NRCS State Conservationist will suggest appropriate 
plan revisions to the RA.
    The RA will make a final decision on the reclamation plan based, in 
part, on its review of NRCS specifications and consideration of 
comments received from the NRCS State Conservationist. The decision 
will be specific to the particular permit under review.
    If a NRCS State Conservationist determines that a revision in the 
State reconstruction specifications is desirable, then NRCS, in 
consultation and cooperation with the RA, will utilize a public 
outreach process to obtain comments on the proposed revision. Under no 
circumstances will the State reconstruction specifications be less 
effective than the National specifications. After a public comment 
process, including publication in the Federal Register and internal 
review by the NRCS and RA, the NRCS State Conservationist will 
incorporate the changes into the specifications and distribute them to 
the NRCS local offices within the State and to the RA. The RA will make 
the revised specifications available to mine operators and other 
interested parties.

Questions and Answers

    NRCS lists below questions related to implementation of NRCS 
specifications which have arisen during their development along with 
answers to those questions.
    Question 1: Are the RA's required to incorporate the NRCS 
specifications into their approved state program through the formal 
amendment process?
    Answer: The RA will use the specifications in making their 
determinations on prime farmland reclamation plans, but they are not 
required to be a part of the approved state program.
    Question 2: What if the RA decides not to incorporate the State 
Conservationist's recommendations into a reclamation plan?
    Answer: The RA is required, under section 510(d)(1) of SMCRA, 30 
U.S.C.1260(d)(1), to consult with the State Conservationist and to 
consider any suggested revisions. It is not mandatory that NRCS 
recommendations be adopted on the permit application and reclamation 
plan. Under the OSM regulations, 30 CFR 823.15, success of prime 
farmland reclamation is based on crop production. NRCS specifications 
are provided to aid the permittee and RA in reviewing and approving 
reclamation plans and in achieving productivity standards. The 
specifications are not performance standards. Section 515(b)(7), 30 
U.S.C. 1265(b)(7), sets forth the general performance standards for 
mining and reclamation activities on prime farmland. Under the OSM 
regulation, the ultimate standard which must be met is the production 
standard. The specifications were not developed to restrict prime 
farmland reclamation, but rather to provide a basis upon which a prime 
farmland reclamation plan can be developed. A reclamation plan that 
differs from the specification can be approved if, in consultation with 
NRCS, the RA determines that a plan takes into consideration the 
particular soil conditions, equipment, and mining reclamation methods 
applicable to a site and will yield the desired results.
    Question 3: The proposed specifications would require permit 
applicants to submit information which may not be required under the 
current RA regulations or in the current permit application form. What 
will be required of the RA's to address this issue?
    Answer: The proposed specifications allow for a variety of options 
in the area of needed information. This approach is consistent with the 
variable site conditions, mining and reclamation equipment, and 
procedures inherent in mining. Individual State RA's will determine 
their informational needs using the NRCS specifications. Some RA's, at 
their discretion, may wish to change permit information requirements.
    Question 4: How will the adoption of the NRCS Soil Reconstruction 
Specifications change the manner in which prime farmland plans are 
currently being approved?
    Answer: Adoption of these specifications will formalize the 
knowledge and expertise that NRCS has brought to prime farmland 
reclamation for over 20 years. State and Federal RA's and mine 
operators have always relied upon the NRCS for technical advice 
relating to prime farmland reconstruction. State RA's have been 
required to consult with NRCS on every acre of non-exempted prime 
farmland which has been mined since enactment of SMCRA. Many State RA's 
with a large amount of prime farmland being mined,

[[Page 57653]]

such as Illinois, have included NRCS in their mine plan review prior to 
the enactment of SMCRA. Because of this long relationship and prior 
history of consultation, most of what will happen after the adoption of 
these specifications will not be new. Formalization of the 
specifications will provide a written framework developed during many 
years of experience and research, from which RA's and permittee can 
operate. The specifications will be available to all who have an 
interest in prime farmland restoration.

Applicability.

    The specifications apply to the removal, stockpiling, replacement, 
and reconstruction of soil materials during surface coal mining and 
reclamation operations on prime farmland, as defined and regulated by 
the Surface Mining Control and Reclamation Act of 1977 (SMCRA), 30 
U.S.C. 1201 et seq.
    These specifications are to be used in conjunction with the 
permanent program performance standards of the Office of Surface Mining 
Regulation and Enforcement, Department of the Interior, which are set 
forth in 30 CFR 785.17, 816.22, and part 823. These specifications 
apply to prime farmlands as defined by the Secretary of Agriculture in 
7 CFR part 657 and historically used for cropland.

Definitions

    The following definitions apply to all documents issued in 
accordance with these specifications, unless specified otherwise:
    Prime farmland means that land which is defined by the Secretary of 
Agriculture in 7 CFR part 657 and which has been historically used for 
cropland.
    Reclamation Plan means the part of a permit application that 
details the actions a mine operator will take to restore the area to be 
mined to an approved post-mining land use.
    Rooting zone means the part of the soil that can be penetrated by 
plant roots. The rooting zone of a soil can be obtained from a 
published NRCS soil survey or determined in the field by a soil 
scientist in accordance with procedures.
    Soil characteristics mean properties of the soil which can be 
described or measured by field or laboratory observations, such as 
color, temperature, water content, structure, pH, and exchangeable 
cations.
    Soil morphology means: a. The physical constitution of a soil 
profile as exhibited by the kinds, thickness, and arrangement of the 
horizons in the profile, and by the texture, structure, consistence, 
and porosity of each horizon; or
    b. The visible characteristics of the soil or any of its parts.
    State regulatory authority means the agency in each State which has 
the primary responsibility at the state level for administering the 
initial or permanent state regulatory program.
    Soil scientist means a technical specialist with the academic 
credentials or work experience which enables the specialist to use 
established procedures to collect the required information about soils.
    Soil survey means field and other investigations which result in a 
map showing the geographic distribution of different kinds of soils and 
an accompanying report that describes, classifies, and interprets such 
soils for use, and which meets the standards of the National 
Cooperative Soil Survey and the procedures of the USDA as incorporated 
by reference in 30 CFR 785.17(c)(1).

Soil removal

Specifications for Designating Prime Farmland Soils for Removal

    a. A soil scientist should locate and mark, on the ground and on 
the plan map, the boundaries of prime farmland soils that will be 
removed during mining. Prime farmland soils on the proposed mining site 
will be identified from a published NRCS soil survey. If a soil survey 
is not available or does not provide the physical, chemical, and 
morphological soil properties described in 30 CFR 785.17(c)(ii), a soil 
scientist should sample and document those properties for the 
identified prime farmland soils using the following procedures:
    i. Soil laboratory analysis for testing any sample will use the 
procedures described in Soil Survey Investigations Report No. 42.
    ii. Identify the rooting zone of the undisturbed prime farmland 
soils in the reclamation plan.
    iii. Identify the original topography of prime farmland soils to be 
mined in the reclamation plan.
    iv. Identify the pre-mining surface and internal drainage 
conditions, flooding frequency, and surface or subsurface drainage 
systems of the prime farmland in the reclamation plan.
    v. Identify the equipment that will be used for soil removal in the 
reclamation plan.

Specifications for Soil Removal.

    a. Soil removal should be accomplished with adherence to the 
following principles;
    i. Minimize pre-mining compaction and destruction of the soil 
structure by using equipment that will have the least impact on the 
natural soil.
    ii. Route soil removal equipment and adjust removal depth with each 
cycle of that equipment to minimize the compaction and destruction of 
soil structure in the natural soil.
    iii. Remove the topsoil layer (A, AP, AE, AB, E horizons and, where 
appropriate, dark noncalcareous Bw and Bt horizons) and, if there is 
not a currently or recently mined area to replace the topsoil, place it 
in a designated stockpile. If the natural topsoil layer is less than 6-
inches thick, remove the top 6 inches of soil and treat it as topsoil. 
The topsoil of prime farmlands may be mixed only if the resulting 
topsoil will have greater potential productivity, as determined using 
the characteristics set forth in Appendix B, than the prime farmland 
topsoil alone. In no case will prime farmland topsoil be mixed with 
topsoil containing rocks larger than 2mm.
    iv. Remove the B horizon and/or C horizon, or an RA approved 
substitute rooting media and, if there is not a currently or a recently 
mined area to concurrently place the rooting media, place it in a 
designated stockpile.
    v. Soil removal should occur only in water state classes that are 
slightly dry or dryer, as defined in the Soil Survey Manual, United 
States Department of Agriculture, Handbook No. 18, October 1993.
    b. Substitution of selected overburden materials for any portion of 
a prime farmland soil is subject to the regulations in 30 CFR 785.17, 
816.22, and part 823. Substitution of any material for naturally 
occurring prime farmland soils should be approved by the RA, in 
consultation with the NRCS, only when the substitute material will have 
a clearly demonstrated productivity potential equivalent to or higher 
than the reconstructed original soil material. This will be based on 
characteristics outlined in Appendix B.

Soil Stockpiling

Specifications For Stockpiling

    Stockpiling is permitted only if the soil removal and 
reconstruction operations cannot be carried out concurrently.
    a. Stockpiled materials should:
    i. Be placed on a stable site within the permit area;
    ii. Be protected from contaminants and unnecessary compaction that 
would interfere with revegetation;
    iii. Be protected from wind and water erosion through prompt 
establishment

[[Page 57654]]

and maintenance of an effective, quick growing vegetative cover or 
through other measures approved by the regulatory authority; and
    (iv) Not be moved until required for redistribution.
    b. Where long-term surface disturbances will result from 
facilities, such as support facilities and preparation plants, and 
where stockpiling of soils would be detrimental to the quality or 
quantity of those soils, the RA may approve the temporary distribution 
of the removed soil materials to an approved site within the permit 
area to enhance the current use of that site until needed for later 
reclamation, provided that diminish the capability of host site and the 
soil material will be retained in a condition more suitable for 
redistribution than if stockpiled.
    c. Sites subject to flooding or slippage are to be avoided for 
stockpiling of soil. The soil survey map for the proposed stockpiling 
site, as well as a field investigation, should be used to determine if 
a proposed soil stockpile location will be subject to flooding or 
slippage.
    d. Ponding of water should be avoided on all stockpiles.
    e. All woody vegetation and any other materials on the stockpile 
site that may degrade the quality of stored material or interfere with 
placement or removal of stockpiled soils should be removed.
    f. The topsoil should be stockpiled separately from the subsoil or 
approved substitute material.
    g. If possible, topsoil and subsoil stockpiles should not be 
located on prime farmland soils. If prime farmland must be used as a 
stockpile site, actions should be taken to avoid and mitigate any 
adverse effects such as compaction.

Soil Replacement and Reconstruction

    Specifications for soil replacement and reconstruction are as 
follows:
    a. The minimum depth of soil and substitute soil material to be 
reconstructed should be 48 inches; or (1) a lesser depth equal to the 
depth of a sub-surface horizon in the natural soil that inhibits or 
prevents root penetration; or (2) a greater depth if determined by the 
RA, in consultation with the NRCS, to be necessary to restore the 
original soil productive capacity.
    b. The rooting zone of the pre-mining soils will be used as a basis 
for determining the replacement soil depth. Appendix A provides 
guidance for establishing the pre-mining rooting zone depth. The depth 
and quality of the rooting zone of the reconstructed prime farmland 
soils should be equal to or greater than the pre-mined soil rooting 
zone. The depth and quality of the replaced subsoil should be verified, 
using characteristics in Appendix B, before replacement of the topsoil.
    c. Topsoil, or the approved substitute material, must be returned 
to the mined area to a thickness not less than that of the pre-mined 
topsoil or to a minimum of 6 inches if the topsoil before mining was 
less than 6 inches thick.
    d. The reconstructed soil should have a hydraulic conductivity, 
texture, porosity, consistency, penetration resistance, and other 
physical properties which approximates the pre-mined soil or are more 
favorable for plant growth as outlined in Appendix B.
    e. The reaction (pH) and other chemical properties of the major 
horizon of the reconstructed soil must be within the ranges of the pre-
mined soil or be more favorable for plant growth. (Appendix B provides 
additional guidance on desirable physical and chemical properties for 
the reconstructed soils).
    f. Final grading of the reconstructed soil should provide for 
adequate surface drainage and for slope gradients within the range of 
the pre-mined prime farmland mapping units. In semi-arid and arid 
regions, surface drainage patterns and slope gradients must be 
reestablished to ensure that reconstructed prime farmland soils receive 
approximately the same amount of surface water run-on from adjacent 
areas as they did in their pre-mined condition.
    g. Soon after topsoil replacement, the soil should be tilled at 
sufficient depth to encourage root and water penetration into the 
subsoil to reduce runoff and erosion.
    h. Erosion control measures contained in the approved reclamation 
plan should be implemented immediately after replacement of the 
topsoil. These erosion control measures should meet, at a minimum, the 
specifications found in Section IV of the local NRCS Field Office 
Technical Guide for seeding, mulching, and other appropriate erosion 
control methods.
    All field observation and testing should be performed by a soil 
scientist or persons under the direction of a soil scientist.

Appendices

Appendix A: Criteria for Determining Pre-Mining Rooting Zone

    Soil horizons are considered as preventing root penetration if 
their physical or chemical properties or water holding capacity cause 
them to prevent penetration by roots of plants common to the area. Soil 
features, e.g. tillage pan, formed during mechanical disturbance are 
not to be considered as root inhibiting for purposes of determining 
pre-mining rooting zone.
    Most prime farmland soils have a favorable rooting depth of at 
least 48 inches and, for such soils, proper soil reconstruction to this 
depth will help in the restoration of productivity. However, there may 
be some prime farmland soils for which reconstruction to a greater 
depth is needed. Where bedrock or approved root inhibiting horizons are 
at a depth of less than 48 inches, reconstruction is thus required to a 
lesser depth. Fragipans or other root inhibiting layers, in order to 
qualify for exclusion from reconstruction, must contribute little or 
nothing to the productive capacity of the soil. This contribution must 
be less than 0.06 inches per inch of available water capacity to 
qualify for such exclusion.
    The rooting zone of the prime farmland soils before mining will be 
determined and documented in the reclamation plan. The rooting zone can 
be obtained from published soil surveys or field determination.
    If a soil survey or field determination (observation of rooting 
depth in an excavation) is not used to determine the rooting zone, the 
following guidelines will be used to determine depth (below 20 inches) 
to a root inhibiting soil layer for each of the following factors.
    Sodium Adsorption Ratio (SAR): This is a measure of the amount of 
sodium (Na+) relative to calcium (Ca+) and 
magnesium (Mg+) in the water extract from saturated soil 
paste. SAR is calculated from the following equation:
[GRAPHIC] [TIFF OMITTED] TN28OC98.017

    Soils having the SAR values listed below will have increased 
dispersion of organic matter and clay particles, reduced permeability 
and aeration, and a degradation of soil structure.

SAR Values
A value of greater than 30 is a root inhibiting soil layer

    Electrical Conductivity: This is a measure of the concentration of 
water soluble salts in a soil (from an extract of saturated soil paste) 
and is used to indicate saline soils. High concentrations of neutral 
salts interfere with the absorption of water by plants because the 
osmotic pressure in the soil solution is higher than that in the plant 
cells. Salts in a soil layer can interfere with the exchange capacity 
of nutrient ions, thereby resulting in nutritional deficiencies in 
plants. Soils having the following value will be root inhibiting:


[[Page 57655]]


A value of greater than 8 mmho/cm.

    Aluminum Saturation: Excess aluminum restricts plant root 
penetration and proliferation in acid subsoils by decreasing water 
uptake in plants. Aluminum toxicities damage roots to the extent that 
they cannot absorb adequate water. High concentrations of aluminum are 
linked to adverse interaction with other elements, e.g., iron and 
calcium. The relationship of aluminum and calcium is the most important 
factor affecting calcium uptake by plants. Aluminum toxicity is linked 
to phosphorus deficiency, and conversely, aluminum tolerance is related 
to the efficient use of phosphorus. A value of equal to or more than 55 
percent aluminum saturation for cotton, peanuts, soybeans, and other 
similar crops and equal to or more than 60 percent aluminum saturation 
for corn, wheat, sorghum, and other similar crops is a root inhibiting 
soil layer using the following equation--
[GRAPHIC] [TIFF OMITTED] TN28OC98.018

    Root Inhibiting Structures: Separations between structural units 
that allow roots to enter have an average spacing of more than 4 inches 
on the horizontal dimension before being considered root inhibiting 
structure. Any of the following soil conditions will be considered a 
root inhibiting soil layer:
    Strong subangular blocky larger than 4 inches or, moderate 
subangular blocky larger than 4 inches or,
    Strong angular blocky larger than 4 inches or, moderate angular 
blocky larger than 4 inches or,
    Prismatic larger than 4 inches or, columnar larger than 4 inches.
    Separations between structural units that allow roots to enter will 
have an average spacing of more than 4 inches on the horizontal 
dimensions before being considered a root inhibiting structure. The 
consistency is always firm or firmer. The kind and size of structure 
and consistency are always evaluated under moderately moist or very 
moist conditions.
    Moist Bulk Density: Bulk density is an indicator of the soil's 
ability for root development, both vertically and horizontally. A soil 
having moist bulk density equal to or more than values shown in table 1 
is considered having a soil root inhibiting layer:

  Table 1.--Root-Limiting Bulk Densities for Each Family Texture Class
------------------------------------------------------------------------
                                                               Rooting-
                                                               limiting
                    Family texture class                         bulk
                                                              density g/
                                                                 cm3
------------------------------------------------------------------------
Sandy......................................................         1.85
Coarse loamy...............................................         1.80
Fine loamy.................................................         1.78
Coarse silty...............................................         1.79
Fine silty.................................................         1.65
Clayey:
    35-45% clay............................................         1.58
    >45% clay..............................................         1.47
------------------------------------------------------------------------

    Soil Strength: Soil strength measurements with the deep-profile 
penetrometer appear to be a viable parameter for assessing rooting 
depth to root inhibiting soil layer when chemical and plant nutritional 
variables are not crop yield-limiting factors. A review of the 
literature for field measurements of soil strength over a period of 
about 15 years has concluded that more field measurements are needed 
before useful limits of soil strength can be established.

Appendix B: Desirable Characteristics for Physical and Chemical 
Properties of Reconstructed Soils

    The reconstructed soils should have the following characteristics. 
These characteristics will help ensure the success of meeting the 
performance standards. Terms used in this Appendix are explained in 
Appendix A.
    All rooting media must meet the following chemical and physical 
properties to have the minimal favorable environment for root growth:
    Sodium Adsorption Ratio 
    [GRAPHIC] [TIFF OMITTED] TN28OC98.019
    
SAR: A value of less than 4.

    Electrical Conductivity:

A value of less than 4 mmho/cm.

    Aluminum Saturation: Aluminum saturation value of less than 20 
percent for cotton, peanuts, soybeans, and other similar crops and less 
than 35 percent aluminum saturation for corn, wheat sorghum, and other 
similar crops using the following equation--
[GRAPHIC] [TIFF OMITTED] TN28OC98.020

    Root Permissive Structure: The reconstructed soil must have a root 
permissive structure after the soil material has been subject to the 
passage of at least 1.5 pore volumes of water in excess of the 
retention at 15 bar bringing all parts through the depth of 
consideration at least one time to very moist or wet. The pore volume 
is obtained by multiplying the depth zones by the water holding 
capacity volume fractions to follow: stratified by family particle-size 
class excluding the effect of those larger than two mm:

------------------------------------------------------------------------
                                                                Volume
                   Family particle size a                      fraction
------------------------------------------------------------------------
Sandy......................................................         0.10
Coarse-loamy...............................................         0.18
Fine-loamy.................................................         0.20
Coarse-silty...............................................         0.25
Fine-Silty.................................................         0.23
Clayey.....................................................        0.15
------------------------------------------------------------------------
a Family particle size classes defined in Soil Taxonomy Agriculture
  Handbook 436.

    Alternative volume fractions may be substituted if documented. The 
volume of water for the family particle-size class is multiplied by the 
thickness of the zone and the amounts of zones are added through to 48 
inches. Under rain fed conditions, the water addition is taken as the 
aggregate of successive monthly positive differences between 
precipitation and the evapotranspiration as computed by an acceptable 
method. Figure 1 is a method for determination of soluble salts and 
percent sodium from extract for identifying dispersive soils. 
Irrigation should be considered when precipitation is insufficient to 
subject the reclaimed soil to the passage of at least one pore volume 
of water while all parts of the soil are very moist or wet. The water 
added must not change the soil solution chemistry from indicative of 
dispersion (zone A in figure 1) to non-dispersive (zone B).
    Figure 1. The field of percent sodium and total dissolved solids, 
both for the saturation extract, divided into a non-dispersive part 
(zone A), a dispersive part (zone B), and a transitional part (zone C). 
From Flanagan, C.P. and G.G.S. Holmgren. 1977. Field methods for 
determination of soluble salts and percent sodium from extract for 
identifying dispersive soils. Am. Soc. Test Mat. STP 623. Reference 
Address: American Society for Testing and Materials (ASTM), 100 Barr 
Harbor Drive, West Conshohcken, PA 19428-2959

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[GRAPHIC] [TIFF OMITTED] TN28OC98.021


    Moist Bulk density is an indicator of the soil's ability for root 
development, both vertically and horizontally. Table 2 has values for 
bulk densities for use during reclamation of mined soils by family soil 
texture classes for nonlimiting to rooting, critical to rooting, and 
root-limiting. As a general rule, reclaimed soils do not have 
continuity of pores or interpedal voids: therefore, values in table 2 
are important consideration during the reconstruction and reclamation 
of mined soils.

         Table 2.--Nonlimiting, Critical, and Root-Limiting Bulk Densities for Each Family Texture Class
----------------------------------------------------------------------------------------------------------------
                                                                                                     Rooting-
                      Family texture class                          Nonlimiting    Critical bulk   limiting bulk
                                                                   bulk density    density g/cm3      density
----------------------------------------------------------------------------------------------------------------
Sandy...........................................................            1.60            1.69            1.85
Coarse loamy....................................................            1.50            1.63            1.80
Fine loamy......................................................            1.46            1.67            1.78
Coarse silty....................................................            1.43            1.67            1.79
Fine silty......................................................            1.34            1.54            1.65
Clayey:
    35-45% clay.................................................            1.40            1.49            1.58
    >45% clay...................................................            1.30            1.39            1.47
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    Caution--Because of the diversity of soil texture, rock fragments, 
climate, mining equipment, and other variables during reclamation, 
moist bulk density values are only a guide. In spite of overall high 
bulk density, there are cases where good root deployment and targeted 
crop yields have been achieved, mainly because the pattern of pore 
spaces was favorable. On the other hand, there are cases in which the 
overall bulk density is not high and good root deployment was expected, 
but a very thin highly compacted layer that could not be detected in a 
standard test method prohibited the entry of plant roots.
    Soil Strength: Soil strength is highly correlated to crop yields on 
reclaimed and reconstructed mined soils. The response is curvilinear 
with crop yield decreasing as soil strength increases. There appears to 
be a lower and upper thresholds to the effect of soil strength on crop 
yield.
    The mechanical impedence is at a minimum at or near 10 PSI. 
Therefore, the rooting volume does not change dramatically below the 
level of 100 PSI. Soil strength with 150 PSI range begins to impact 
rooting, and in the range of 280 PSI is root-limiting. Even though a 
reconstructed mined soil has nonlimiting soil strength for rooting, a 
significant difference in crop yield may occur compared to the soils on 
the permit area prior to mining. It must be understood that the quality 
of subsoil material, which is replaced during reconstruction and 
reclamation as well as reclamation practices, will become a dominate 
influence to any further increase in yield for soils having non-
limiting soil strength. The PSI values are determined by inserting into 
the soil profile a 3/4 inch rod with a 300 right circular cone point 
welded to the end of the rod.

    Signed at Washington, D.C. on October 15, 1998.
Pearlie S. Reed,
Chief, Natural Resources Conservation Service.
[FR Doc. 98-28467 Filed 10-27-98; 8:45 am]
BILLING CODE 3410-16-P