Learn about the soil data in Transect, including prime farmland, hydric soils, bedrock depth, and hydrologic rating.
Soil conditions are essential factors to consider in renewable energy projects, particularly ground-mounted solar. Transect leverages the USDA Gridded Soil Survey Geographic (gSSURGO) Database to offer valuable soil data. This information helps assess constructability, saturation, hydric classification, erosion hazard, and other key characteristics that can impact the stability, durability, and environmental footprint of your project.
In this article, we’ll review:
- How to View Soil Data in the Map
- How to View Soil Data in the Report Map
- Prime Farmland
- Hydric Soils
- Bedrock Depth
- Hydrologic Rating
Viewing Soil Data in the Map
You can use the following Map Layers for a preliminary snapshot of an area’s soil data:
- Soil Map (Bedrock Depth - Minimum)
- Soil Map (Hydric Rating)
- Soil Map (Hydrologic Group - Dominant Conditions)
- Prime Farmland in CONUS (2021)
Viewing Soil Data in the Report Map
At the top of the Executive Summary is the Report Map, where you can apply layers to visualize certain aspects of your Area of Interest. After running a report, you showcase the findings within your AOI by toggling layers for Farmland Classification, Bedrock Depth (ft), Hydrologic Group, Soil Hydric Rating, and Soils.
You can also navigate to Supporting Docs & Resources > Setting > Soils for a full breakdown of your area’s findings. Within the data table, you can select a soil type to visualize it on the Map.
Prime Farmland Definitions and Locations
Prime farmland is the most suitable land for growing crops like food, feed, forage, fiber, and oilseeds because it has the ideal physical and chemical properties for these uses. Because of its importance, prime farmland might need to be considered in federal or local permits.
A note from our Environmental Experts: Prime Farmland is important because there are many local regulations that protect prime farmland and farmland of statewide importance for certain types or thresholds of development, particularly in agricultural-rich communities. At the federal level, the Farmland Protection Policy Act of 1981 applies if projects plan to permanently convert farmland (directly or indirectly) to non-agricultural uses. This law affects federal agencies and those receiving federal support.
Within the “Soils” table, the Farm Class column indicates if an area is considered prime farmland.
Several categories may apply to soils on your project:
- Prime Farmland: land that has the best physical and chemical characteristics for producing food, feed, forage, fiber, and oilseed crops and is also available for these uses. This may trigger additional permitting requirements in federal NEPA documents and some state or local permits.
- Unique Farmland: Land other than prime farmland that is used for the production of specific high-value food and fiber crops, such as citrus, tree nuts, olives, cranberries, and other fruits and vegetables
- Farmland of Statewide Importance: Soils that nearly meet the requirements for prime farmland and economically produce high crop yields when treated and managed according to acceptable farming methods.
- Not Prime Farmland: Soils that do not meet any qualifications for special designation.
Hydric Soils
Within the “Soils” table, the Hydric Rating column indicates whether or not a map unit component is classified as hydric soil.
A note from our Environmental Experts: Hydric soils are important because they indicate that wetlands may be present on a site. When hydric soils are viewed alongside NWI wetland or NHD stream data, it helps to inform a developer of the likelihood that significant wetlands exist onsite prior to contracting a full wetland delineation. Even if there are little to no NWI wetlands or NHD streams mapped out, there may still be a cause for concern if there are significant hydric soils within an AOI.
- Hydric means that all major and minor components listed for a given map unit are rated hydric.
- Predominantly Hydric means that all significant components listed for a given map unit are rated as hydric, and at least one contrasting minor component is not rated hydric.
- Partially Hydric means that at least one major component listed for a given map unit is rated as hydric, and at least one other major component is not rated hydric.
- Predominantly Nonhydric means that no significant component listed for a given map unit is rated as hydric, and at least one contrasting minor component is rated hydric.
- Nonhydric means no major or minor components for the map unit are rated hydric. The assumption is that the map unit is nonhydric even if none of the components within the map unit have been rated.
Bedrock Depth
Within the "Soils" table, the Bedrock Depth - Minimum column highlights areas where bedrock may be a concern. The depth shown below is calculated in centimeters.
In the Report Map, Bedrock Depth is shown in feet instead of centimeters.
A note from our Environmental Experts: Depth to bedrock is an important soil attribute to consider, as an AOI with bedrock at or near the soil surface could present some considerable construction challenges.
Hydrologic Group
Within the "Soils" table, the Hydrologic Group - Dominant Conditions column provides a rating to indicate runoff potential and soil saturation levels. 
A note from our Environmental Experts: Hydrologic Group--Dominant Conditions is an important soil feature to consider, as this attribute estimates the amount of runoff a soil will produce when it is saturated, which could also present some significant construction challenges.
The Hydrologic Group, designated A, B, C, or D, indicates the expected amount of runoff from saturated soil.
- Group A: Soils with high infiltration rates, such as deep, well-drained sands and gravels. These soils have low runoff potential.
- Group B: Soils with moderate infiltration rates, typically moderately deep and well-drained. Runoff potential is moderate.
- Group C: Soils with slow infiltration rates, often due to restrictive layers or fine textures. Runoff potential is higher than Group B.
- Group D: Soils with very slow infiltration rates, such as clayey soils or those with high water tables. Runoff potential is highest.