Soil Characteristics

Generally speaking, the soil on the homestead is suitable for use as pasture and little else. The presence of clay and a high water table complicate construction, especially of any subsurface structures (e.g., basements, cisterns, etc.).

The US Department of Agriculture has developed a National Cooperative Soil Survey. The map below shows the types of soil at various places on the farm. The table that follows identifies the soil types identified on the map.

soil-map

soil-composition

Use of the Soil Survey

The soil survey informs decisions about land use for building, agriculture, waste disposal, and other factors. Each soil type is assessed in terms of composition and surface features (e.g., slope) to determine the suitability for specific uses. Note that soil features may not necessarily preclude certain activities but may require special care be taken in planning, design, and implementation to accommodate soil deficiencies and to mitigate their effects.

Building Construction

Soil affects building construction in terms of the effects of the soil on corrosion of steel and concrete and on the suitability of the soil for basements.

Risk of Corrosion

Corrosion of Concrete

“Risk of corrosion” pertains to potential soil-induced electrochemical or chemical action that corrodes or weakens concrete. The rate of corrosion of concrete is based mainly on the sulfate and sodium content, texture, moisture content, and acidity of the soil. Special site examination and design may be needed if the combination of factors results in a severe hazard of corrosion. The concrete in installations that intersect soil boundaries or soil layers is more susceptible to corrosion than the concrete in installations that are entirely within one kind of soil or within one soil layer.

Risk of concrete corrosion in 73136 and 73018 is high.

Corrosion of Steel

“Risk of corrosion” pertains to potential soil-induced electrochemical or chemical action that corrodes or weakens uncoated steel. The rate of corrosion of uncoated steel is related to such factors as soil moisture, particle-size distribution, acidity, and electrical conductivity of the soil. Special site examination and design may be needed if the combination of factors results in a severe hazard of corrosion. The steel in installations that intersect soil boundaries or soil layers is more susceptible to corrosion than the steel in installations that are entirely within one kind of soil or within one soil layer.

Risk of corrosion of uncoated steel is high for 73136 and moderate for 73018.

Suitability for Basements

Dwellings are single-family houses of three stories or less. For dwellings with basements, the foundation is assumed to consist of spread footings of reinforced concrete built on undisturbed soil at a depth of about 7 feet.

The ratings for dwellings are based on the soil properties that affect the capacity of the soil to support a load without movement and on the properties that affect excavation and construction costs. The properties that affect the load-supporting capacity include depth to a water table, ponding, flooding, subsidence, linear extensibility (shrink-swell potential), and compressibility. Compressibility is inferred from the Unified classification of the soil. The properties that affect the ease and amount of excavation include depth to a water table, ponding, flooding, slope, depth to bedrock or a cemented pan, hardness of bedrock or a cemented pan, and the amount and size of rock fragments.

The ratings are both verbal and numerical. Rating class terms indicate the extent to which the soils are limited by all of the soil features that affect the specified use. “Not limited” indicates that the soil has features that are very favorable for the specified use. Good performance and very low maintenance can be expected. “Somewhat limited” indicates that the soil has features that are moderately favorable for the specified use. The limitations can be overcome or minimized by special planning, design, or installation. Fair performance and moderate maintenance can be expected. “Very limited” indicates that the soil has one or more features that are unfavorable for the specified use. The limitations generally cannot be overcome without major soil reclamation, special design, or expensive installation procedures. Poor performance and high maintenance can be expected.

Suitability of soils for basements in 73136 and 73018 is very limited.

Building Construction Summary

Proposed home sites are on soils in Map Units 73136 and 73018.

Map Unit 73136 presents high risk of corrosion to both concrete and uncoated steel. Suitability for basements is very limited due to high water table, hard pan, and high clay content resulting in high potential for soil shrinkage and swelling.

Map Unit 73018 presents high risk of concrete corrosion and moderate risk of corrosion of uncoated steel. Like 73136, 73018 presents challenges to construction of buildings with below-ground components.

Basement construction at all proposed home sites will require special techniques to prevent water intrusion and structural damage.

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