1. (a)

   1. (1) The depth to seasonal water tables of three (3) durations can be determined from the following guides.
   2. (2) The guides are interpretations of the type of redoximorphic features present in a horizon.
   3. (3) Each horizon should be placed in the most limiting SWT class for which the criteria are met.
   4. (4) All colors are for moist conditions.

2. (b)

   1. (1) The placing of soil horizons into SWT classes based on redoximorphic features is an interpretation and requires some understanding of soil development processes.
   2. (2) Redoximorphic features are not expected to occur unless the horizon has been both saturated and anoxic conditions have led to reduction of iron and manganese.

   3. (3) Reduction of iron and manganese is not expected to occur until:

      1. (A) After the horizon has been saturated for a few days or weeks; and
      2. (B) The saturation has been periodic or continuous for a substantial period of time (decades or centuries).

   4. (4) Brief. Soil horizons which have seasonal water tables of brief duration contain one (1) or more of the following:

      1. (A) Concentrations or depletions with chroma greater than or equal to three (≥3);
      2. (B) Less than twenty percent (20%) of the mass is chroma three (3) depletions; or
      3. (C) Two percent (2%) or more black manganese (Mn) masses.

   5. (5) Moderate. Soil horizons which have seasonal water tables of moderate duration contain one (1) or more of the following:

      1. (A) Depletions with chroma less than or equal to two (≤2) comprise less than fifty percent (50%) of the mass; or
      2. (B) Chroma three (3) depletions comprise more than twenty percent (20%) of the mass.
   6. (6) Long. Soil horizons which have seasonal water tables of long duration contain chroma less than or equal to two (≤2) in fifty percent (50%) or more of the mass.

3. (c)

   1. (1) Soil horizons that have chroma and value of less than or equal to three (≤3) due to high organic matter contents (A horizons) present problems for SWT interpretations.
   2. (2) Also, with low chroma comprised of uncoated grains which result from prolonged leaching with organic acids (E horizons) are not considered to be an indication of an SWT.
   3. (3) These horizons (A and E) shall be considered to contain SWTs only if they also contain identifiable redox concentrations and/or depletions.
   4. (4) A plowed horizon (Ap), which has chroma of three (3) or less, shall not be considered to contain an SWT unless the first underlying horizon contains an SWT.
   5. (5) The duration of the SWT in a plowed horizon (Ap) with chroma less than or equal to three (≤3) and in A and E horizons with chroma less than or equal to (≤3) and redox concentrations and/or depletions shall be the same as in the first underlying horizon.

4. (d) Monitoring requirements.

   1. (1)

      1. (A) Some soils may exhibit redoximorphic features that are not indicative of current soil conditions.
      2. (B) In such soils, monitoring wells or piezometers may be necessary to determine current soil wetness conditions.
      3. (C) Monitoring shall be done during the wet season.

   2. (2)

      1. (A) A property owner or their representative has the option to use observation wells and/or piezometers to demonstrate that redoximorphic features are not an indication of zones of saturation.
      2. (B) The following procedures for the use of observations wells/piezometers to evaluate the depth and duration of seasonal water tables shall be implemented.
   3. (3) The property owner or their representative shall notify the Department of Health, in writing, of the intent to use observation wells and/or piezometers to evaluate depth and duration of seasonal water tables.

   4. (4)

      1. (A) On individual lots, at least one (1) observation well and/or piezometer shall be installed and monitored on a site within both the proposed primary and secondary absorption areas.
      2. (B) If, in the judgment of the department, more than one (1) is needed, the property owner or their representative shall be notified.
      3. (C) For subdivision evaluation, at least one (1) observation well and/or piezometer shall be installed in each soil mapping unit.
      4. (D) However, a minimum of one (1) observation well and/or piezometer per acre is required.

   5. (5)

      1. (A) The wells and/or piezometers shall extend at least thirty-six inches (36”) into the natural soil.
      2. (B) The department reserves the right to determine the depth of all wells and/or piezometers.
      3. (C) In soils with a fragipan, the observation well and/or piezometer shall not be installed deeper than the top of the fragipan.
   6. (6) All plans and specifications for observation wells/piezometers shall be submitted and installed under the supervision of a professional soil classifier.
   7. (7) Monitoring of seasonal water tables shall be conducted by a professional soil classifier or designated representative.
   8. (8) Under no circumstances will the property owner/developer be allowed to monitor the water levels.

   9. (9)

      1. (A) The monitoring period shall be during the wet season (December 1 through May 15 of the following year) to verify the depth and duration of the seasonal water tables.
      2. (B) Monthly precipitation during the monitoring period should be near the long-term (thirty-year) average.
      3. (C) The department may not accept data from the monitoring period if the deviation from average is substantial.
      4. (D) Several methods are available to document deviation of monthly and seasonal precipitation from average conditions.
      5. (E) Precipitation data used should be from the nearest weather station.
      6. (F) The monitoring period shall be eight (8) consecutive weeks and two (2) nonconsecutive days per week.
      7. (G) A minimum of sixteen (16) recorded observations shall be conducted.
   10. (10) At its discretion, the department shall field check the monitoring periodically during the time of expected saturated soil conditions.

   11. (11)

       1. (A) The department may, at any time during the observation period, verify the observed water depth by conducting a soil boring next to, and of equal depth with, any of the observation wells/piezometers.
       2. (B) The well may be declared invalid by the department if the water level, after twenty-four (24) hours without precipitation, presents a discrepancy with the observed water level in the data collected.
       3. (C) The owner will be notified by the department of such findings.

   12. (12)

       1. (A) When monitoring determines that the site is suitable, the department will request that a new site evaluation be submitted.
       2. (B) The monitoring information shall be incorporated into the new site evaluation.

   13. (13)

       1. (A) Some soils have been extensively studied and have no contemporary seasonal water tables.
       2. (B) These specific areas may be exempted from the soil redoximorphic features but shall be sized by hydraulic conductivity or percolation rates.

5. (e) Lowering seasonal water tables.

   1. (1) Interceptor drains.

      1. (A) Interceptor drains can be utilized to lower the brief seasonal water table to a maximum depth of eighteen inches (18”) in soils less than thirty percent (30%) clay on sites with three percent (3%) or more slope.
      2. (B) No reduction is allowed in the moderate seasonal water table.

   2. (2) Capping fill.

      1. (A) The depth of the observed seasonal water table may be increased by a factor equal to half the depth of the settled fill up to a maximum adjustment of seven inches (7”).
      2. (B) Capping fills are outlined in 14 CAR § 21-707.
      3. (C) Systems incorporating capping fills shall be designed to load to the surface of the settled cap in order to utilize the adjustment credited for the applied cap.

Codification Notes: “SWT” means seasonal water table.