Engineering
This section provides information for planning land uses related to urban development and to water management. Soils are rated for various uses, and the most limiting features are identified. Ratings are given for building site development, sanitary facilities, construction materials, and water management. The ratings are based on observed performance of the soils and on the estimated data and test data in the "Soil Properties" section.
Information in this section is intended for land use planning, for evaluating land use alternatives, and for planning site investigations prior to design and construction. The information, however, has limitations. For example, estimates and other data generally apply only to that part of the soil within a depth of 5 or 6 feet. Because of the map scale, small areas of different minor components may be included within the mapped areas of a specific soil.
The information is not site specific and does not eliminate the need for onsite investigation of the soils or for testing and analysis by personnel experienced in the design and construction of engineering works.
Government ordinances and regulations that restrict certain land uses or impose specific design criteria were not considered in preparing the information in this section. Local ordinances and regulations should be considered in planning, in site selection, and in design.
Soil properties, site features, and observed performance were considered in determining the ratings in this section. During the fieldwork for this soil survey, determinations were made about grain-size distribution, liquid limit, plasticity index, soil reaction (pH), depth to bedrock, hardness of bedrock within 5 or 6 feet of the surface, soil wetness, depth to a seasonal high water table, slope, likelihood of flooding, natural soil structure aggregation, and soil density. Data were collected about kinds of clay minerals, mineralogy of the sand and silt fractions, and the kinds of adsorbed cations. Estimates were made for erodibility, permeability, corrosivity, shrink-swell potential, available water capacity, and other behavioral characteristics affecting engineering uses.
This information can be used to evaluate the potential of areas for residential, commercial, industrial, and recreational uses; make preliminary estimates of construction conditions; evaluate alternative routes for roads, streets, highways, pipelines, and underground cables; evaluate alternative sites for sanitary landfills, septic tank absorption fields, and sewage lagoons; plan detailed onsite investigations of soils and geology; locate potential sources of gravel, sand, earth fill, and topsoil; plan drainage systems, irrigation systems, ponds, terraces, and other structures for soil and water conservation; and predict performance of proposed small structures and pavements by comparing the performance of existing similar structures on the same or similar soils.
The information in the tables, along with the soil maps, the soil descriptions, and other data provided in this survey, can be used to make additional interpretations.
Some of the terms used in this soil survey have a special meaning in soil science and are defined in the Glossary.
Soil properties influence the development of building sites, including the selection of the site, the design of the structure, construction, performance after construction, and maintenance. Tables 14 and 15 show the degree and kind of soil limitations that affect dwellings with and without basements, small commercial buildings, local roads and streets, shallow excavations, and lawns and landscaping.
The ratings in the tables are both descriptive and numerical. Rating class terms indicate the extent to which the soils are limited by all of the soil features that affect building site development. Slight indicates that the soil has features that are very favorable for the specified use. Good performance and very low maintenance can be expected. Moderate 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. Severe 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.
Numerical ratings in the tables indicate the severity of individual limitations. The ratings are shown as decimal fractions ranging from 0.00 to 1.00. They indicate gradations between the point at which a soil feature has the greatest negative impact on the use (1.00) and the point at which the soil feature is not a limitation (0.00).
Dwellings and small commercial buildings
Major management factors
Dwellings are single-family houses of three stories or less. For dwellings without basements, the foundation is assumed to consist of spread footings of reinforced concrete built on undisturbed soil at a depth of 2 feet or at the depth of maximum frost penetration, whichever is deeper. 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 soil wetness, ponding, flooding, subsidence, linear extensibility (LEP or shrink-swell potential), and compressibility. Compressibility is inferred from the Unified classification. The properties that affect the ease and amount of excavation include depth to soil wetness, ponding, flooding, slope, depth to bedrock or a cemented pan, hardness of bedrock or a cemented pan, and the amount, size, and depth of fragments.
Small commercial buildings are structures that are less than three stories high and do not have basements. The foundation is assumed to consist of spread footings of reinforced concrete built on undisturbed soil at a depth of 2 feet or at the depth of maximum frost penetration, whichever is deeper. The ratings 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 soil wetness, ponding, flooding, subsidence, linear extensibility (LEP or shrink-swell potential), and compressibility (which is inferred from the Unified classification). The properties that affect the ease and amount of excavation include flooding, depth to a water table, ponding, slope, depth to bedrock or a cemented pan, hardness of bedrock or a cemented pan, and the amount, size, and depth of fragments.
Major management considerations- dwellings without basements
Depth to bedrock: Depth to bedrock is shallow enough to cause a restriction in use.
Flooding: Soil flooded by moving water from stream overflow, runoff, or high tides.
Organic matter (OM): High organic matter percent at some depth, sometimes expressed as a Unified soil class (PT, OL, or OH), can result in poor engineering properties and subsidence. Low organic matter can influence plant growth.
Ponding: Standing water on soils in closed depressions that is removed only by percolation or evapotranspiration.
Shrink-swell (LEP): The shrinking of soil when dry and the swelling when wet is expressed as the linear extensibility percent (LEP). Shrinking and swelling can damage roads, dams, building foundations, and other structures. It can also damage plant roots.
Slope: The slope is steep enough that special practices are required to ensure satisfactory performance of the soil.
Wetness: Wetness near the surface or high water tables affect growth of plants and construction of facilities.
Major management considerations- dwellings with basements
Depth to bedrock: Depth to bedrock is shallow enough to cause a restriction in use.
Flooding: Soil flooded by moving water from stream overflow, runoff, or high tides
Fragments: The profile contains enough fragments of specific size to adversely affect site preparation or trafficability.
Ponding: Standing water on soils in closed depressions that is removed only by percolation or evapotranspiration.
Shrink-swell (LEP): The shrinking of soil when dry and the swelling when wet is expressed as the linear extensibility percent. Shrinking and swelling can damage roads, dams, building foundations, and other structures. It can also damage plant roots.
Slope: The slope is steep enough that special practices are required to ensure satisfactory performance of the soil.
Wetness: Wetness near the surface or high water tables affect growth of plants and construction of facilities.
Major management considerations- small commercial buildings
Depth to bedrock: Depth to bedrock is shallow enough to cause a restriction in use.
Flooding: Soil flooded by moving water from stream overflow, runoff, or high tides
Fragments: The profile contains enough fragments of specific size to adversely affect site preparation or trafficability.
Ponding: Standing water on soils in closed depressions that is removed only by percolation or evapotranspiration.
Shrink-swell (LEP): The shrinking of soil when dry and the swelling when wet is expressed as the linear extensibility percent. Shrinking and swelling can damage roads, dams, building foundations, and other structures. It can also damage plant roots.
Slope: The slope is steep enough that special practices are required to ensure satisfactory performance of the soil.
Wetness: Wetness near the surface or high water tables affect growth of plants and construction of facilities.
Major management factors
Local roads and streets have an all-weather surface and carry automobile and light truck traffic all year. They have a subgrade of cut or fill soil material; a base of gravel, crushed rock, or soil material stabilized by lime or cement; and a surface of flexible material (asphalt), rigid material (concrete), or gravel with a binder. The ratings are based on the soil properties that affect the ease of excavation and grading and the traffic-supporting capacity. The properties that affect the ease of excavation and grading are depth to bedrock or a cemented pan, hardness of bedrock or a cemented pan, depth to soil wetness, ponding, flooding, the amount of coarse fragments, and slope. The properties that affect the traffic-supporting capacity are soil strength (as inferred from the AASHTO group index number), subsidence, linear extensibility (LEP or shrink-swell potential), the potential for frost action, depth to a water table, and ponding.
Major management considerations
AASHTO GI(soil strength): Engineering properties of the soil expressed as the AASHTO Group Index indicate soil strength. Values > 8 indicate low soil strength for roads and airfield construction.
Depth to bedrock: Depth to bedrock is shallow enough to cause a restriction in use.
Flooding: Soil flooded by moving water from stream overflow, runoff, or high tides
Ponding: Standing water on soils in closed depressions that is removed only by percolation or evapotranspiration.
Shrink-swell (LEP): The shrinking of soil when dry and the swelling when wet is expressed as the linear extensibility percent. Shrinking and swelling can damage roads, dams, building foundations, and other structures. It can also damage plant roots.
Slope: The slope is steep enough that special practices are required to ensure satisfactory performance of the soil.
Wetness: Wetness near the surface or high water tables affect growth of plants and construction of facilities.
Shallow excavations are trenches or holes dug to a maximum depth of 5 or 6 feet for graves, utility lines, open ditches, or other purposes. The ratings are based on the soil properties that influence the ease of digging and the resistance to sloughing. Depth to bedrock or a cemented pan, hardness of bedrock or a cemented pan, the amount of coarse fragments, and dense layers influence the ease of digging, filling, and compacting. Depth to the seasonal soil wetness, flooding, and ponding may restrict the period when excavations can be made. Slope influences the ease of using machinery. Soil texture, depth to soil wetness, and linear extensibility (LEP or shrink-swell potential) influence the resistance to sloughing.
Major management factors
The ease of digging, filling, and compacting is affected by the depth to bedrock, a cemented pan, or a very firm dense layer; coarse fragment content; soil texture; and slope. The time of the year that excavations can be made is affected by the depth to a seasonal high water table and the susceptibility of the soil to flooding. The resistance of the excavation walls or banks to sloughing or caving is affected by soil texture and depth to the water table.
Major management considerations- shallow excavations
Bulk density (dense layer): A soil layer has a bulk density that results in a soil that is too dense.
Caving potential: The walls or sides of excavations tend to cave inwards. All soil excavations have a potential to cave, but some soils have a higher potential than others do.
Clay or clayey texture: At some depth there is a clay content or clayey texture that results in soil that is slippery and sticky when wet and slow to dry.
Depth to bedrock: Depth to bedrock is shallow enough to cause a restriction in use.
Flooding: Soil flooded by moving water from stream overflow, runoff, or high tides.
Fragments: The profile contains enough fragments of specific size to adversely affect site preparation or trafficability.
Ponding: Standing water on soils in closed depressions that is removed only by percolation or evapotranspiration.
Slope: The slope is steep enough that special practices are required to ensure satisfactory performance of the soil.
Wetness: Wetness near the surface or high water tables affect growth of plants and construction of facilities.
Tables 16 and 17 show the degree and kind of soil limitations that affect septic tank absorption fields, sewage lagoons, sanitary landfills, and daily cover for landfill. The ratings are both descriptive and numerical. Rating class terms indicate the extent to which the soils are limited by all of the soil features that affect these uses. Slight indicates that the soil has features that are very favorable for the specified use. Good performance and very low maintenance can be expected. Moderate 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. Severe 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.
Numerical ratings in the tables indicate the severity of individual limitations. The ratings are shown as decimal fractions ranging from 0.00 to 1.00. They indicate gradations between the point at which a soil feature has the greatest negative impact on the use (1.00) and the point at which the soil feature is not a limitation (0.00).
Major management factors
Septic tank absorption fields are areas in which effluent from a septic tank is distributed into the soil through subsurface tiles or perforated pipe. Only that part of the soil between depths of 24 and 60 inches is evaluated. The ratings are based on the soil properties that affect absorption of the effluent, construction and maintenance of the system, and public health. Permeability, depth to a water table, ponding, depth to bedrock or a cemented pan, and flooding affect absorption of the effluent. Stones and boulders, ice, and bedrock or a cemented pan interfere with installation. Subsidence interferes with installation and maintenance. Excessive slope may cause lateral seepage and surfacing of the effluent in downslope areas.
Some soils are underlain by loose sand and gravel or fractured bedrock at a depth of less than 4 feet below the distribution lines. In these soils the absorption field may not adequately filter the effluent, particularly when the system is new. As a result, the ground water may become contaminated.
Major management considerations
Depth to bedrock: Depth to bedrock is shallow enough to cause a restriction in use.
Flooding: Soil flooded by moving water from stream overflow, runoff, or high tides
Permeability: The movement of water through the soil adversely affects the specified use. The permeability may be either too slow or too fast.
Ponding: Standing water on soils in closed depressions that is removed only by percolation or evapotranspiration.
Slope: The slope is steep enough that special practices are required to ensure satisfactory performance of the soil.
Wetness: Wetness near the surface or high water tables affect growth of plants and construction of facilities.
Major management factors
Sewage lagoons are shallow ponds constructed to hold sewage while aerobic bacteria decompose the solid and liquid wastes. Lagoons should have a nearly level floor surrounded by cut slopes or embankments of compacted soil. Nearly impervious soil material for the lagoon floor and sides is required to minimize seepage and contamination of ground water. Considered in the ratings are slope, permeability, depth to a water table, ponding, depth to bedrock or a cemented pan, flooding, coarse fragments, and content of organic matter.
Soil permeability is a critical property affecting the suitability for sewage lagoons. Most porous soils eventually become sealed when they are used as sites for sewage lagoons. Until sealing occurs, however, the hazard of pollution is severe. Soils that have a permeability rate of more than 2 inches per hour are too porous for the proper functioning of sewage lagoons. In these soils, seepage of the effluent can result in contamination of the ground water. Ground-water contamination is also a hazard if fractured bedrock is within a depth of 40 inches, if soil wetness is high enough to raise the level of sewage in the lagoon, or if floodwater overtops the lagoon.
A high content of organic matter is detrimental to proper functioning of the lagoon because it inhibits aerobic activity. Slope, bedrock, and cemented pans can cause construction problems, and coarse fragments can hinder compaction of the lagoon floor. If the lagoon is to be uniformly deep throughout, the slope must be gentle enough and the soil material must be thick enough over bedrock or a cemented pan to make land smoothing practical.
Major management considerations
Depth to bedrock: Depth to bedrock is shallow enough to cause a restriction in use.
Flooding: Soil flooded by moving water from stream overflow, runoff, or high tides
Organic matter (OM): High organic matter percent at some depth, sometimes expressed as a Unified soil class (PT, OL, or OH), can result in poor engineering properties and subsidence. Low organic matter can influence plant growth.
Permeability: The movement of water through the soil adversely affects the specified use. The permeability may be either too slow or too fast.
Ponding: Standing water on soils in closed depressions that is removed only by percolation or evapotranspiration.
Slope: The slope is steep enough that special practices are required to ensure satisfactory performance of the soil.
Wetness: Wetness near the surface or high water tables affect growth of plants and construction of facilities.
Sanitary landfills are areas where solid waste is disposed of by burying it in soil. There are two types of landfill—trench and area. In a trench landfill, the waste is placed in a trench. It is spread, compacted, and covered daily with a thin layer of soil excavated at the site. In an area landfill, the waste is placed in successive layers on the surface of the soil. The waste is spread, compacted, and covered daily with a thin layer of soil from a source away from the site.
Both types of landfill must be able to bear heavy vehicular traffic. Both types involve a risk of ground-water pollution. Ease of excavation and revegetation should be considered.
Major management factors
A trench sanitary landfill is an area where solid waste is placed in successive layers in an excavated trench. The waste is spread, compacted, and covered daily with a thin layer of soil excavated at the site. When the trench is full, a final cover of soil material at least 2 feet thick is placed over the landfill. The ratings in the table are based on the soil properties that affect the risk of pollution, the ease of excavation, trafficability, and revegetation. These properties include permeability, depth to bedrock or a cemented pan, depth to soil wetness, ponding, slope, flooding, texture, stones and boulders, highly organic layers, soil reaction (pH), and content of salts and sodium. Unless otherwise stated, the ratings apply only to that part of the soil within a depth of about 6 feet. For deeper trenches, onsite investigation may be needed.
Hard, nonrippable bedrock, creviced bedrock, or highly permeable strata in or directly below the proposed trench bottom can affect the ease of excavation and the hazard of ground-water pollution. Slope affects construction of the trenches and the movement of surface water around the landfill. It also affects the construction and performance of roads in areas of the landfill.
Soil texture and consistence affect the ease with which the trench is dug and the ease with which the soil can be used as daily or final cover. They determine the workability of the soil when dry and when wet. Soils that are plastic and sticky when wet are difficult to excavate, grade, or compact and are difficult to place as a uniformly thick cover over a layer of refuse.
The soil material used as the final cover for a trench landfill should be suitable for plants. It should not have excess sodium or salts and should not be too acid. The surface layer generally has the best workability, the highest content of organic matter, and the best potential for plants. Material from the surface layer should be stockpiled for use as the final cover.
In an area sanitary landfill, solid waste is placed in successive layers on the surface of the soil. The waste is spread, compacted, and covered daily with a thin layer of soil from a source away from the site. A final cover of soil material at least 2 feet thick is placed over the completed landfill. The ratings in the table are based on the soil properties that affect trafficability and the risk of pollution. These properties include flooding, permeability, depth to soil wetness, ponding, slope, and depth to bedrock or a cemented pan.
Flooding is a serious problem because it can result in pollution in areas downstream from the landfill. If permeability is too rapid or if fractured bedrock, a fractured cemented pan, or the water table is close to the surface, the leachate can contaminate the water supply. Slope is a consideration because of the extra grading required to maintain roads in the steeper areas of the landfill. Also, leachate may flow along the surface of the soils in the steeper areas and cause difficult seepage problems.
Major management considerations- trench sanitary landfill
Clay or clayey texture: At some depth there is a clay content or clayey texture that results in soil that is slippery and sticky when wet and slow to dry.
Depth to bedrock: Depth to bedrock is shallow enough to cause a restriction in use.
Flooding: Soil flooded by moving water from stream overflow, runoff, or high tides
Permeability: The movement of water through the soil adversely affects the specified use. The permeability may be either too slow or too fast.
Ponding: Standing water on soils in closed depressions that is removed only by percolation or evapotranspiration.
Salinity (EC): Excess water-soluble salts in the soil restricts the growth of most plants.
Sand or sandy texture: At some depth there is a sand content or sandy texture that results in soil that is soft and loose, droughty, and low in fertility or is too fine to use as gravel.
Sodicity (SAR): Excess exchangeable sodium, which imparts poor physical properties restricts the growth of plants.
Slope: The slope is steep enough that special practices are required to ensure satisfactory performance of the soil.
Sodicity (SAR): Excess exchangeable sodium, which imparts poor physical properties restricts the growth of plants.
Wetness: Wetness near the surface or high water tables affect growth of plants and construction of facilities.
Major management considerations- area sanitary landfill
Depth to bedrock: Depth to bedrock is shallow enough to cause a restriction in use.
Flooding: Soil flooded by moving water from stream overflow, runoff, or high tides
Permeability: The movement of water through the soil adversely affects the specified use. The permeability may be either too slow or too fast.
Ponding: Standing water on soils in closed depressions that is removed only by percolation or evapotranspiration.
Slope: The slope is steep enough that special practices are required to ensure satisfactory performance of the soil.
Wetness: Wetness near the surface or high water tables affect growth of plants and construction of facilities.
Major management factors
Daily cover for landfill is the soil material that is used to cover compacted solid waste in an area sanitary landfill. The soil material is obtained offsite, transported to the landfill, and spread over the waste. The ratings in the table also apply to the final cover for a landfill. They are based on the soil properties that affect workability, the ease of digging, and the ease of moving and spreading the material over the refuse daily during wet and dry periods. These properties include soil texture, depth to soil wetness, ponding, rock fragments, slope, depth to bedrock or a cemented pan, soil reaction (pH), and content of salts, sodium, or lime.
Loamy or silty soils that are free of large stones and excess gravel are the best cover for a landfill. Clayey soils may be sticky and difficult to spread; sandy soils are subject to wind erosion.
Slope affects the ease of excavation and of moving the cover material. Also, it can influence runoff, erosion, and reclamation of the borrow area.
After soil material has been removed, the soil material remaining in the borrow area must be thick enough over bedrock, a cemented pan, or soil wetness to permit revegetation. The soil material used as the final cover for a landfill should be suitable for plants. It should not have excess sodium, salts, or lime and should not be too acid.
Major management considerations
Clay or clayey texture: At some depth there is a clay content or clayey texture that results in soil that is slippery and sticky when wet and slow to dry.
Depth to bedrock: The bedrock is too near the surface.
Fragments: The profile contains enough fragments of specific size to adversely affect site preparation or trafficability.
Packing: Unified classes of OL, OH, CH, or MH indicate that soil may be difficult to compact using regular earthwork construction equipment.
Organic matter (OM): High organic matter percent at some depth, sometimes expressed as a Unified soil class (PT, OL, or OH), can result in poor engineering properties and subsidence. Low organic matter can influence plant growth.
Permeability: The movement of water through the soil adversely affects the specified use. The permeability may be either too slow or too fast.
pH: The pH of the soil is too low (acid) or too high (basic) for most plant growth.
Ponding: Standing water on soils in closed depressions that is removed only by percolation or evapotranspiration.
Salinity (EC): Excess water-soluble salts in the soil restricts the growth of most plants.
Sand or sandy texture: At some depth there is a sand content or sandy texture that results in soil that is soft and loose, subject to wind erosion, droughty, and low in fertility or is too fine to use as gravel.
Slope: The slope is steep enough that special practices are required to ensure satisfactory performance of the soil.
Sodicity (SAR): Excess exchangeable sodium, which imparts poor physical properties restricts the growth of plants.
Wetness: Wetness near the surface or high water tables affect growth of plants and construction of facilities.
Tables 18 and 19 give information about the soils as potential sources of gravel, sand, topsoil, reclamation material, and roadfill. Normal compaction, minor processing, and other standard construction practices are assumed.
The soils are rated good, fair, or poor as potential sources of topsoil, reclamation material, and roadfill. The features that limit the soils as sources of these materials are specified in the tables. The numerical ratings given after the specified features indicate the degree to which the features limit the soils as sources of topsoil, reclamation material, or roadfill. The lower the number, the greater the limitation.
The soils are rated as a good or poor source of sand and gravel. A rating of good means that the source material is likely to be in or below the soil. The numerical ratings in these columns indicate the degree of probability. The number 0.00 indicates that the soil is an improbable source. A number between 0.00 and 1.00 indicates the degree to which the soil is a probable source of sand or gravel.
Sand and gravel are natural aggregates suitable for commercial use with a minimum of processing. They are used in many kinds of construction. Specifications for each use vary widely. In table 18, only the probability of finding material in suitable quantity is evaluated. The suitability of the material for specific purposes is not evaluated, nor are factors that affect excavation of the material. The properties used to evaluate the soil as a source of sand or gravel are gradation of grain sizes, the thickness of suitable material, and the content of rock fragments. If the lowest layer of the soil contains sand or gravel, the soil is rated as a probable source regardless of thickness. The assumption is that the sand or gravel layer below the depth of observation exceeds the minimum thickness.
Topsoil is used to cover an area so that vegetation can be established and maintained. The upper 40 inches of a soil is evaluated for use as topsoil. Also evaluated is the reclamation potential of the borrow area. The ratings are based on the soil properties that affect plant growth; the ease of excavating, loading, and spreading the material; and reclamation of the borrow area. Toxic substances, soil reaction (pH), and the properties that are inferred from soil texture, such as available water capacity and fertility, affect plant growth. The ease of excavating, loading, and spreading is affected by rock fragments, slope, depth to a water table, soil texture, and thickness of suitable material. Reclamation of the borrow area is affected by slope, depth to a water table, rock fragments, depth to bedrock or a cemented pan, and toxic material.
The surface layer of most soils is generally preferred for topsoil because of its organic matter content. Organic matter greatly increases the absorption and retention of moisture and nutrients for plant growth.
Reclamation material is used in areas that have been drastically disturbed by surface mining or similar activities. When these areas are reclaimed, layers of soil material or unconsolidated geological material, or both, are replaced in a vertical sequence. The reconstructed soil favors plant growth. The ratings in the table do not apply to quarries and other mined areas that require an offsite source of reconstruction material. The ratings are based on the soil properties that affect erosion and stability of the surface and the productive potential of the reconstructed soil. These properties include the content of sodium, salts, and calcium carbonate; soil reaction (pH); available water capacity; erodibility; texture; content of rock fragments; and content of organic matter and other features that affect fertility.
Roadfill is soil material that is excavated in one place and used in road embankments in another place. In this table, the soils are rated as a source of roadfill for low embankments, generally less than 6 feet high and less exacting in design than higher embankments.
The ratings are for the whole soil, from the surface to a depth of about 5 feet. It is assumed that soil layers will be mixed when the soil material is excavated and spread.
The ratings are based on the amount of suitable material and on soil properties that affect the ease of excavation and the performance of the material after it is in place. The thickness of the suitable material is a major consideration. The ease of excavation is affected by coarse fragments, depth to soil wetness, and slope. How well the soil performs in place after it has been compacted and drained is determined by its strength (as inferred from the AASHTO classification of the soil) and linear extensibility (shrink-swell potential).