Environmental Engineering Reference
In-Depth Information
science references, an asterisk (*) is placed next to the term in the Field Indicators
glossary. Familiarity with the following terms (presented in the Field Indicators
glossary) is necessary for the identification of Field Indicators.
1. Depleted matrix - This is an important concept used in many of the Field
Indicators. Note that all depleted matrices must have values
4 and chromas
2, and depending on the value and chroma, may or may not need the presence
of redox concentrations.
2. Gleyed matrix - The definition of a gleyed matrix for the purposes of the Field
Indicators are different than the definition used in Soil Taxonomy. For the
purposes of the Field Indicators, a gleyed matrix has colors found on the gleyed
pages of the Munsell Book of Color and also must have a value
4.
3. Layer(s) - A soil horizon and a layer for the purposes of the Field Indicators are
not synonymous. There can be multiple layers in the same horizon if that horizon
meets all the requirements of two different layers and is thick enough to meet the
combined thicknesses requirements of the both layers. There can also be multiple
horizons that meet all the requirements of the same layer except thickness that can
be combined to meet the thickness requirements. For a good explanation of
combining horizons to meet the thickness requirement, see Chapter 3 of any
Corps of Engineers Regional Supplement (
http://www.usace.army.mil/Missions/
4. LRR and MLRA - Field Indicators are regionalized. Identification of the LRR
(and in some cases what MLRA the sites occurs in) for the site in question is critical
as it limits the Field Indicators valid for that site. Figure
4.10
is a map of the
LRRs. MLRA identification can be obtained from:
http://soils.usda.gov/survey/
5. Organic soil material - Use of the Field Indicators require a distinction between
organic soil material and mineral soil material. Some Field Indicators also
require the distinction between the grades of decomposition (muck, mucky
peat, or peat).
6. Within - When a Field Indicator states that a layer must start within a certain
depth, if the layer starts at that depth it is considered to be within that depth.
4.10.3 Concepts and Rules
In addition, a clear understanding of the following concepts is inherent to the proper
application of the Field Indicators:
1. The Field Indicators are proof positive. If a soil meets a Field Indicator, it is a
hydric soil. If it does not meet an indicator, it is still a hydric soil if it meets the
definition.
2. A soil must meet the requirements in the indicator description to meet that Field
Indicator. User notes are provided to assist in the interpretation of those
requirements.
