(b) The hydraulic conductivity class may be determined using the following:

1. (1) High hydraulic conductivity. Natural soil horizons which have not been compacted by human activities, especially vehicle traffic and tillage operations, and are in the following particle size classes:

   1. (A)

(i) Sandy.

1. (ii) The texture of the fine earth fraction (less than two millimeters (<2 mm) diameter particles) is sand or loamy sand but not loamy very fine sand.

   1. (iii) Rock fragments comprise less than thirty-five percent (35%) of the horizon volume;

   2. (B)

      1. (i) Fragmental.
      2. (ii) Rock fragments (stones, cobbles, gravel, and very coarse sand particles) comprise ninety percent (90%) or more of the horizon volume.
      3. (iii) Too little fine earth to fill some of the interstices larger than one millimeter (1 mm); and

   3. (C)

      1. (i) Sandy-skeletal.
      2. (ii) Rock fragments two millimeters (2 mm) in diameter or larger make up thirty-five percent (35%) or more but less than ninety percent (90%) of the horizon volume;
      3. (iii) Enough fine earth to fill interstices larger than one millimeter (1 mm); and
      4. (iv) The fine earth fraction is sandy as defined for the sandy particle size class;

2. (2) Moderate hydraulic conductivity.

   1. (A) Natural soil horizons which clearly have some soil structure other than platy, which have not been compacted by human activities, especially vehicle traffic and tillage operations, and which have one (1) of the following textural classes:

      1. (i) Sandy loam;
      2. (ii) Loam;
      3. (iii) Silt loam;
      4. (iv) Silt;
      5. (v) Sandy clay loam;
      6. (vi) Clay loam;
      7. (vii) Silty clay loam; or
      8. (viii) Rock fragment content of less than ninety percent (90%).

   2. (B)

      1. (i) Soils with sandy clay, clay, or silty clay texture and that are low shrink-swell will be considered to have moderate hydraulic conductivity.
      2. (ii) These residual soils have a hue of 5YR or redder and have typically formed over limestone and chert parent materials associated with the Ozark Highlands in northern Arkansas.
      3. (iii) Alluvial soils such as those deposited by the Arkansas and Red Rivers and red soils formed from other types of parent materials and/or in other parts of the state are not included in this exception.
      4. (iv) See Appendix I for additional guidance for identification of soils meeting these criteria;

3. (3) Low hydraulic conductivity — Forty percent to sixty percent (40% – 60%) clay.

   1. (A) Included are soil horizons which have platy structure or are massive and horizons which have been compacted by human activities, especially vehicle traffic and tillage operations.

   2. (B) Also included are horizons with one (1) of the following textural classes:

      1. (i) Sandy clay;
      2. (ii) Clay;
      3. (iii) Silty clay; and
      4. (iv) Rock fragment content is less than ninety percent (90%);
4. (4) Red soil chart, see Appendix I; and
5. (5) No loading rates are available for low hydraulic conductivity soils with greater than sixty percent (60%) clay.