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What is a Soil Survey?

Photo of the Greater Delta area AlaskaA soil survey is a resource inventory where field scientists collect, organize, and interpret information about the natural resources in an area.  Although the main focus is on soils, data is also collected on vegetation, landforms, and surface hydrology.

Field scientists conduct the survey by walking across the landscape and observing differences in soil types, as well as the vegetation, landform, and hydrology associated with each soil type.  Field scientists use hand tools to dig hundreds of holes during the course of a soil survey to observe and record the properties of the different soils.  Data on various resources is described at each site.

Photo of a soil pitThe holes are usually about 6 feet deep and about 2 feet wide.  Whenever they can, soil scientists make use of cutbanks, gravel pits, and other exposures to see the soil from the side.

When done with the hole, the field scientist fills it in and replaces the vegetation.  It is usually difficult to tell where the holes were dug.

The results of a soil survey are maps showing the location and arrangement of the different soil types.  Tables and databases show the properties of the soils, their potential uses, and their limitations. The vegetation and hydrology associated with each soil type is described.

Soil Survey is a Cooperative Venture

A Soil Survey is sponsored by cooperative agreement between land owners and managers, community organizations and the NRCS. A Memorandum of Understanding formalizes this agreement and outlines the specifications, timeframes, and products for the survey. NRCS provides the basic survey crew and technical expertise.  Cooperators are asked to provide whatever assistance they can, such as access to their lands, publicity about the survey, room and board for the survey crew, resource data, and knowledge about the trails, roads, and rivers in their area.  Any financial assistance provided by cooperators will be used to increase the number of survey crews and accelerate the completion of the project. Cooperators can be any organization with responsibility for land and resource use and management, or interest in resource data products.

Prior to the survey's completion, NRCS will release interim products and once the survey is done, electronic datasets, maps, and publications. Within the project area, data will be collected at various levels of detail.  Villages, transportation corridors, and other selected lands will be mapped in detail.  Remote areas will be mapped at broader scales. No lands will be accessed or surveyed unless the land owner grants permission.  Cooperators may identify certain lands, such as cultural sites, that will have restricted or no access for survey work.

What sort of information will a soil survey provide?

  • Maps that show the location and arrangement of the soils.  On the example below, taken from the Eklutna area of the Anchorage Soil Survey, black lines drawn on an aerial photograph represent boundaries between soil types.  The symbols refer to particular types of soil that are identified in the survey.

Image of a soil survey map

  • Tables that show the different soil properties.  This information can be used by land managers, engineers, planners, and others to make land use decisions and to design and locate projects.  All terms used in the various reports are explained in the glossary that appears at the end of the survey manuscript.
Image of a physical and chemical properties table

A sample from the table of Physical and Chemical properties included in soil surveys.

  • Tables that provide ratings on the suitability of limitations of each soil type for various purposes.  An example is shown below. This soil would not be an appropriate location for septic tank absorption fields or sewage lagoons.

Image of a sanitary facilities table

A sample from the table showing potential use of the soil for septic tank
absorption fields and sewage lagoons and the limitations associated with the soil.

  • Tables that provide data related to:

    Building Site Development (suitability for constructing buildings)
    Construction Source Materials (sources of sand, gravel, topsoil)
    Engineering Properties & Classification
    Physical and Chemical Properties of the Soil
    Physical Analysis of Selected Soils
    Chemical Analysis of Selected Soils
    Sanitary Facilities (suitability of soil for sewage or landfill waste disposal)
    Soil and Water Features
    Vegetation types (Ecological Sites)
    Off-road Vehicle and Foot Trails
    Hydric Soils (wetland soils) information
    Forest Management
  • Soil Surveys also provide a lot of useful information about the general nature of an area including geology, vegetation, and climate.

What are the Uses of a Soil Survey?

As a planner or resource manager you already have good knowledge about the lands your community depends on.  A soil survey is a unique opportunity to get basic information about those lands and also their current condition.  A soil survey will provide information that will help you locate septic systems or sewage lagoons, roads, buildings, airstrips, playgrounds, or landfills. A soil survey will identify soils that are subject to erosion and compaction so that logging operations with skid trails and landings can be made less costly.  A soil survey will identify the depth to water tables, potential gravel and sand sources, as well as topsoil and roadfill sources.  A soil survey will help identify the best lands for various wildlife habitats, or for subsistence plants; or for forestry, grazing, and agriculture. These are just some of the uses of a soil survey.  A soil survey is a valuable resource and can make your planning easier and potentially better adapted to local conditions.  It can provide you with information on the current condition of the land so that you can measure changes that may occur from new land uses.