TSSH Part 618
Determinations and Delineations of Hydric Soils
Hydric soils determinations or delineations are typically completed as part of a wetland determination or delineation. They are also used to identify areas that were once wetlands but that, as a result of alterations in hydrology or soils, no longer meet the three defining parameters of a wetland (hydrophytic vegetation, wetland hydrology, and hydric soils). Determinations are made to establish the presence or absence of hydric soils on a site, and delineations are made to establish the spatial distribution of hydric soils on a site.
Wetland determinations are completed on agricultural land to identify areas that are subject to Swampbuster provisions in the National Food Security Act Manual (NFSAM) in order to establish eligibility for USDA program benefits.
Wetland determinations and delineations may also be completed in areas that may qualify for USDA programs designed to protect and conserve wetlands, such as the Wetland Reserve Program, or in areas that may be subject to Section 404 of the Clean Water Act (CWA). Some NRCS State Offices may also have agreements with State and local agencies to provide technical assistance for State and local wetland programs.
Identification of hydric soils in areas that are no longer wetlands may be required to determine whether the areas qualify for USDA conservation programs and practices that need wetland restoration or enhancement components. In some cases, a delineation identifying the boundary between hydric and nonhydric soils is needed to establish the extent and boundary of the area containing hydric soils where wetland restoration would be most effective. In many cases, hydric soils may be the only observable parameter left.
Responsibilities of the resource soil scientist (618.01)
NRCS technical soil services for hydric soil determinations are conducted on agricultural lands for USDA program purposes when requested by USDA program participants. Additionally, determinations can be made when there is a memorandum of understanding or a cooperative agreement with a Federal, State, or local form of government.
On February 25, 2005, NRCS and the U.S. Army Corps of Engineers (COE) released Joint Guidance from the NRCS and the COE Concerning Wetland Determinations for the Clean Water Act and the Food Security Act Manual. This document outlines the responsibilities of NRCS and the COE for doing wetland determinations. NRCS completes all wetland determinations on agricultural lands for participants or persons intending to become participants in USDA programs when the proposed activity involves draining, dredging, filling, leveling, or otherwise manipulating the land, as defined in the NFSAM. The participant’s activities must be for the purpose of, or have the effect of making possible, the production of an agricultural commodity. An agricultural commodity is any crop planted and produced by annual tilling of the soil, including tilling by one-trip planters, and sugarcane. NRCS determinations pertain only to compliance with the Food Security Act for USDA program participants.
Resource soil scientists may be called upon to teach the hydric soils portion of local training courses by local agreements between NRCS and the COE. Joint training between NRCS and the COE is provided by the agencies for their field personnel involved in wetland determinations and delineations. A portion of the training involves the identification and delineation of hydric soils.
Resource soil scientists may also be requested to provide technical assistance on hydric soil determinations and delineations for COE field personnel for purposes of the Clean Water Act (CWA). Because agreements between NRCS and the COE may vary from State to State, resource soil scientists should always know and follow their State Office policy when they provide wetlands assistance to anyone outside the NRCS. For CWA purposes, the COE field person is responsible for making the final decision regarding classifying and labeling jurisdictional wetlands.
Some NRCS State Offices may have joint agreements with State and local agencies to provide technical services and training to State and local field personnel involved in wetland determinations and delineations.
Collecting data for hydric soils determinations (618.02)
All hydric soils must meet the criteria defined by the National Technical Committee for Hydric Soils (NTCHS). That is, a hydric soil is a soil that forms under the conditions of saturation, flooding, or ponding long enough during the growing season to develop anaerobic conditions in the upper part. Hydric soil field indicators and a hydric soil technical standard have been developed to determine whether a soil meets the criteria for hydric soils.
The following definition of hydric soils is outlined in the NFSAM (514.4): “Hydric soils are defined as soils that, in an undrained condition, are saturated, flooded, or ponded long enough during a growing season to develop an anaerobic condition that supports the growth and regeneration of hydrophytic vegetation” (7 CFR 12.2).
Database selection criteria have been established to query the NASIS database to identify soil map unit components that are likely to be hydric soils. However, hydric soils lists should not be used in the field to make hydric soil determinations.
Most hydric soils determinations are done through the use of field indicators of hydric soils. Field indicators are morphological features that can be seen in the soil or smelled to determine that a hydric soil is present. “The publication Field Indicators of Hydric Soils in the United States (USDA, NRCS) will be applied to identify and delineate soils that would meet the definition of a hydric soil in the field” (NFSAM 514.4). Procedures for describing and sampling soils and a list of the field indicators are available at the NTCHS Web site.
Procedures for describing and sampling soils and a list of the field indicators to determine hydric soils for purposes of Section 404 of the CWA are available in the Corps of Engineers 1987 Wetlands Delineation Manual and associated regional supplements. Field indicators used for NFSAM and CWA purposes are the same where regional supplements to the 1987 manual have been approved and implemented.
When a soil fails to meet a hydric soil indicator but is thought to meet the hydric soil definition, the hydric soil technical standard can be used to determine whether or not the soil is hydric. Long-term site monitoring is required to confirm that the soil is saturated and becomes anaerobic in the upper part. In some cases, reference data that satisfy the hydric soils technical standard from a similar soil may be used to support a hydric soil determination. Soils that fail to meet an indicator and may require the use of the technical standard include: a) soils with problematic parent materials that do not exhibit typical hydric soil morphology, b) soils developed in environments that suppress the development of typical hydric soil morphology, and c) young soils that have not had the time to develop hydric soil morphology.
The data collection form (see Exhibit 618-1) is tailored for collecting pedon data for hydric soils. All pedon data collected should be entered in Pedon PC. This form is provided as an option.
Documentation during hydric soil determinations (618.03)
It is important to document the characteristics of both hydric and nonhydric soils onsite when hydric soil determinations are made. This documentation can be used to further refine the hydric/nonhydric soil boundary throughout the site. A data sheet should be completed for both hydric and nonhydric soil components of a site. If multiple wetlands exist on a property, a data sheet for the hydric component of each wetland should be filled out. Also, if multiple soil components (soil series or higher taxa) are located in a wetland or the immediately adjacent upland, a data sheet should be completed for each separate component.
In completing the data sheet, make sure to document all characteristics that will assist in identifying and confirming whether the soil meets a recognized indicator (“Field Indicators of Hydric Soils in the United States”). These characteristics include, but are not limited to, detailed information on soil color, texture, redoximorphic features, and organic features in the soil. Also, depth and thickness of soil characteristics are important in the use of field indicators, so a tiling spade should be used to excavate an intact slice of soil during the process of evaluating and describing the upper part of the soil.
The hydric soil boundary should be recorded on an aerial photograph, farm plan map, soil survey map, or some other base map. Data collection points must also be recorded on the base map, and, when possible, the GPS-measured latitude and longitude or UTM of data points should be recorded. The hydric soils boundary may be determined by the use of field data as well as offsite observations of aerial photography, soil survey maps, topography maps, wetland inventory maps, old farm plan maps, Farm Service Agency slides, and/or any other available information.
It is also important to document soil characteristics that affect water movement through the soil. Such characteristics as saturated hydraulic conductivity and depth to confining (restrictive) layers are important when a site is evaluated for wetland creation or restoration. These characteristics are important when equipment is installed to evaluate whether a soil meets criteria of the hydric soil technical standard as well as the Technical Standard for Water-Table Monitoring of Potential Wetland Sites.
Wetland determinations conducted for NFSAM purposes may be appealed through the USDA appeals process. The COE also has an appeals process for wetland determinations. Although not all hydric soil determinations will be appealed or litigated, it is important to remember that the documentation taken during routine hydric soils determinations must be adequate to withstand a legal appeal or litigation.
Expert services related to judicial requests involving hydric soils that originate as a result of actions affecting Federal, State, or local governments involved with wetlands require agency advice and NRCS management approval and USDA legal counsel authority before the services are provided. Contact the NRCS State Administrative Officer (SAO) if expert legal services are requested.
NRCS programs and practices for which hydric soil determinations may be needed (618.04)
The most common reason to provide conservation technical assistance for wetland identification on agricultural lands is to determine wetland conservation compliance and provide producers with information about what they can or cannot do concerning the degree of installation and maintenance of drainage systems, including ditches, tiles, and other drains. Specific programs that may require the identification of hydric soils include the Conservation Reserve Program (CRP), Environmental Quality Incentives Program (EQIP), Wildlife Habitat Incentives Program (WHIP), and Wetland Reserve Program.
Practices that may require identification of hydric soils include constructed wetlands, shallow water development, wildlife management, spring development, wetland creation, wetland enhancement, wetland restoration, wetland wildlife habitat management, prescribed grazing-wetland practice, riparian buffer management, surface and subsurface drainage, livestock/irrigation ponds, and improvement and management of stream habitat. Other practices may also require the identification of hydric soils to ensure proper design and effectiveness.
Hydric soil determinations and wetland determinations completed by NRCS for NFSAM purposes do not apply to COE or other agencies’ jurisdictions. When determinations are certified by NRCS for NFSAM purposes, the land owner must be informed that the determination/delineation may not be valid for identifying the extent of jurisdiction for COE CWA purposes.
Cooperator programs and practices for which hydric soil determinations are required (618.05)
The Bureau of Land Management, Forest Service, National Park Service, Bureau of Indian Affairs, Department of Defense, and other National Cooperative Soil Survey (NCSS) land management agencies are required to comply with Section 404 of the Clean Water Act. The COE must issue permits for discharge of dredged or fill material into waters of the United States, including wetlands. Guidelines of the Council on Environmental Quality state that the COE and the EPA will review all Environmental Impact Statements (EIS) on direct Federal proposals involving discharge of dredged or fill material, and the EIS must contain requisite information on discharges and be consistent with EPA guidelines for discharges under subsection 404(b)(1).
Executive Order 11990 directs that each agency “shall provide leadership and shall take action to minimize the destruction, loss or degradation of wetlands, and to preserve and enhance the natural and beneficial values of wetlands in carrying out the agency's responsibilities for (1) acquiring, managing, and disposing of Federal lands and facilities; and (2) providing Federally undertaken, financed, or assisted construction and improvements; and (3) conducting Federal activities and programs affecting land use, including but not limited to water and related land resources planning, regulating, and licensing activities.”
Practices that may require hydric soils determinations to establish whether potential wetlands might be involved include spring and other water development projects; road construction; construction of recreation or other facilities; wetland enhancement, restoration, and alteration; stream habitat improvement projects; granting rights of way; energy and minerals permitting and sales; land disposal; allotment management planning; timber sale planning; and wildlife habitat planning.
Other information that may be needed (618.06)
By definition, a hydric soil needs only to be formed under anaerobic conditions in the upper part. Therefore, a hydric soil may not currently function as a hydric soil if the soil or hydrology has been altered enough that the soil no longer develops anaerobic conditions in the upper part. It is important to document evidence of contemporary vs. relict soil morphology and other evidences of disturbance. This documentation aids in establishing the presence of a hydric soil resulting from contemporary or past water table levels. These data may also be used to confirm that the wetland hydrology parameter is met when a wetland determination is completed.
Where manmade drainage systems have been utilized or are proposed, scope and effect equations can be used to estimate the drainage effect. Soil parameters used in scope and effect calculations may be needed to determine whether a site has been effectively drained to the point that it no longer qualifies as a wetland.
Resource soil scientists may also be called upon to assist in the development of wetland functional assessment models. These models use wetland physical characteristics to rapidly assess the wetland’s ability to function in such roles as surface and shallow subsurface water storage, particulate retention (physical processes), organic carbon export, cycling of nutrients, removal of elements and compounds (biogeochemical processes), maintenance of characteristic plant communities, and maintenance of characteristic wildlife habitat. Characteristics used to model the ability of a wetland to function include such soil characteristics as texture, clay content, organic matter content, color, redoximorphic features, presence of restricting layers, pH, salinity, and evidence of compaction.
In many cases wetland determinations are made by an interdisciplinary team of technical experts. The other specialists provide expertise into site vegetation and hydrology; however, if the other site parameters (hydrophytic vegetation and wetland hydrology) are uncomplicated or the site is severely altered and hydric soil is the only observable parameter, a resource soil scientist may be called upon to do wetland delineations without assistance. Requirements for meeting the other two parameters and protocols for sampling can be found in the Wetland Determination section of the NFSAM. Requirements for Farm Bill determinations and for purposes of Section 404 of the CWA are provided in the 1987 COE Wetlands Delineation Manual and supplements.
National Technical Committee for Hydric Soils. 2007. Altered soils. Hydric Soils Tech Note 13.
National Technical Committee for Hydric Soils. 2007. Hydric Soils—Introduction.
National Technical Committee for Hydric Soils. 2007. The hydric soil technical standard. Hydric Soils Tech. Note 11.
Schoeneberger, P.J., D.A. Wysocki, E.C. Benham, and W.D. Broderson (eds.). 2002. Field book for describing and sampling soils. Natural Resources Conservation Service, National Soil Survey Center, Lincoln, NE.
U.S. Army Corps of Engineers. CFR 40 Part 230 Section 404(b)(1). Guidelines for specification of disposal sites for dredged or fill material.
U.S. Army Corps of Engineers. 1987. Corps of Engineers wetlands delineation manual. Waterways Experiment Station Technical Report Y-87-1. Vicksburg, MS.
U.S. Army Corps of Engineers. 2005. Technical standard for water-table monitoring of potential wetland sites. ERDC TN-WRAP-05-2.
U.S. Army Corps of Engineers. 2007. Regional supplements to Corps Delineation Manual.
U.S. Department of Agriculture. 2008. National Food Security Act Manual. 4th Edition.
U.S. Department of Agriculture, Natural Resources Conservation Service. National Technical Committee for Hydric Soils (Web site).
U.S. Department of Agriculture, Natural Resources Conservation Service. Wetland assessment.
U.S. Department of Agriculture, Natural Resources Conservation Service. 2010. Field indicators of hydric soils in the United States, version 7.0. L.M. Vasilas, G.W. Hurt, and C.V. Noble, eds. USDA/NRCS in cooperation with the National Technical Committee for Hydric Soils, Fort Worth, TX.
U.S. Department of Agriculture, Natural Resources Conservation Service. 2007. National soil survey handbook. Part 655. Technical Soil Services.
U.S. Department of Agriculture, Natural Resources Conservation Service. 2007. Scope and effect equations.
U.S. Department of Agriculture, Natural Resources Conservation Service. 2007. Title 440—Programs: Part 510—Appeals and Mediation Subpart A—General Information.
U.S. Department of Agriculture, Natural Resources Conservation Service. 2007. Wetland conservation provisions (Swampbuster).
U.S. Department of Agriculture, Natural Resources Conservation Service, Conservation and Ecosystems Assistance Division. 2007. National Food Security Act Manual, 3rd Edition. Part 513—Preparing to Make Wetland Determinations or Delineations.
U.S. Department of Agriculture, Natural Resources Conservation Service and Office of the Chief, and U.S. Department of the Army. February 25, 2005. Guidance on conducting wetland determinations for the Food Security Act of 1985 and Section 404 of the Clean Water Act. Washington, DC.
U.S. Environmental Protection Agency. 1977. Clean Water Act, Section 404.
U.S. Environmental Protection Agency. 1977. Executive Order 11990. 42 F.R. 26961.
Other useful information (618.08)
Mid-Atlantic Committee for Hydric Soils.
New England Technical Committee for Hydric Soils. New England field indicators.
U.S. Army Corps of Engineers. Engineer Resource and Development Center. Environmental Laboratory. Publications.
U.S. Army Corps of Engineers, Wetland Regulatory Program.
U.S. Department of Agriculture. Wetlands information.
U.S. Environmental Protection Agency. Wetlands information.
Detailed Hydric Soil Description Form (Exhibit 618-1)