Mining Specifications for Prime Farmland

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

[[Page 57656]]

[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