Section II November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Use and Explanation of Soil Interpretations The basis for this section is the Map Unit Interpretation Record (MUIR), which is created by combining the Map Unit Record (SOI-6) and Soil Interpretation Record (SIR). This information is stored in the State Soil Survey Database (SSSD). SSSD contains current information for each map unit which has been edited or "tailored" by state and area specialists to represent local ranges in the data. Soil survey interpretations are predictions of soil behavior for specified land uses and specified management practices. They are based on the soil properties that directly influence the specified use of the soil. Soil survey interpretations allow users of soil surveys to plan reasonable alternatives for the use and management of soils. They are used to plan both broad categories of land use, such as cropland, pastureland, woodland, or urban development, as well as specific elements of those land uses, for example, irrigation of cropland, equipment use in woodland management, or septic tank absorption fields. The Highly Erodible Lands table and the Hydric Soils Table have not been included in this report. Also, the Prime Farmland report in this publication is not the official Field Office copy. When soil interpretations are used in connection with delineated soil areas on soil maps, the information pertains to the soil for which the soil area is named. Other soils that are in areas too small to map may occur within the delineated area. The interpretations ordinarily do not apply to the included soils. More detailed studies are required if small, specific sites are to be developed or used within a given soil delineation. For example, a soil delineation bearing the name Loring silt loam, 1 to 3 percent slopes, also can include small, unmappable areas of other soils, such as Calloway and Henry soils. The interpretations apply to the Loring part of the delineated soil area and not to the included soils. Soil interpretations will not eliminate the need for onsite study and testing of specific sites for the design and construction for specific uses. They can be used as a guide to planning more detailed investigations and for avoiding undesirable sites for an intended use. The soil map and interpretations can be used to select sites that have the least limitations for an intended use. No consideration was given in these interpretations to the size and shape of soil delineations nor to the pattern they form with other soils on the landscape. For example, some very desirable soil areas are too small, too irregular in shape, or occur with less desirable soils in a pattern too complex for the intended use. Although not considered in the interpretations, these items may influence the final selection of a site. Section II November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Explanation of Key Phrases Used In Soil Interpretations Soil interpretations typically list the degree of limitation or suitability and factors affecting use of the soil for agricultural and nonagricultural purposes. The interpretations apply to the soils in their natural site (unless indicated otherwise) and not for areas that are altered by cut-or-fill operations. Limitation or suitability terms used are as follows: Slight (or good) - relatively free of limitations or limitations are easily overcome. Moderate (or fair) - limitations need to be recognized, but can be overcome with good management or careful design. Severe (or poor or very poor) - limitations are difficult or costly to overcome. Explanation of key phrases used are as follows: Factors affecting Explanation Area reclaim Borrow areas hard to reclaim. Cemented pan Cemented pan too close to surface. Complex slope Slopes short and irregular. Cutbanks cave Wall of cuts not stable. Deep to water Deep to permanent water table during dry season. Dense layer A very firm layer difficult to dig. Depth to rock Bedrock too close to surface. Droughty Soil cannot hold enough water. Dusty Soil particles detach easily and cause dust. Erodes easily Water erodes soil easily. Excess fines Contains too much silt and clay. Excess gypsum Contains too much gypsum. Excess humus Contains too much organic matter. Excess lime Carbonates restrict plant growth. Excess salt Water-soluble salts may restrict plant growth. Excess sulphur Excessive amount of sulphur in the soil may cause extreme acidity. Fast intake Water infiltrates rapidly. Favorable Features of soil favorable. Section II November 1, 1995 Explanation of key phrases - Continued Factors affecting Explanation Flooding Soil temporarily floods by stream overflow, runoff, or high tide. Fragile Soil that is easily damaged by use or disturbance. Frost action Freezing and thawing can damage structures. Hard to pack Difficult to compact. Large stones Rock fragments 10 inches or larger. Low strength Soil not strong enough to adequately support loads. No water Too deep to ground water. Percs slowly Water moves through the soil too slowly. Piping Water may form tunnels or pipelike cavities in the soil. Ponding Standing water on soils in closed depressions. Poor filter Because of rapid permeability, the soil may not adequately filter effluent. Poor outlets Difficult or expensive to install outlets for drainage. Rooting depth Soil is thin over layer that greatly restricts root growth. Seepage Water moves through soil or fractured bedrock too fast. Shrink-swell Soil expands significantly on wetting and shrinks on drying. Slippage Soil mass susceptible to movement downslope, when loaded, excavated, or wet. Slope Slope is too great. Slow intake Water infiltration restricted. Slow refill Ponds fill slowly because of restricted soil permeability. Small stones Contains many rock fragments less than 10 inches across. Soil blowing Soil easily moved by wind. Subsides Settlement of organic soils or of soil containing semifluid layers. Thin layer Inadequate thickness of suitable soil. Too acid Soil is so acid that growth of plants is restricted. Too arid Soil is too dry most of the time. Too clayey Soil slippery and sticky when wet and slow to dry. Too sandy Soil soft and loose; droughty and low in fertility. Toxicity Excessive amount of toxic substances, such as aluminum or sulphur. Unstable fill Banks of fill likely to cave or slough. Wetness Soil wet during period of use. Section II-ii-A November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Nontechnical Soil Description Nontechnical soil descriptions describe soil properties or management considerations specific to a soil map unit or group of map units. These descriptions are written in terminology that nontechnical users of soil survey information can understand. Nontechnical soil descriptions are a powerful tool for creating reports. These high quality, easy to read reports can be generated by conservation planners and other SCS employees for distribution to land users. These descriptions are available with both CAMPS and SSSD. Soil map unit descriptions and map unit interpretation records (MUIR) are the basis for these descriptions. The following categories or land uses are examples of descriptions which are commonly used in CAMPS and SSSD. SOI - soil characteristics description SO5 - soil interpreation record description AGR - agronomic description ENG - engineering description RNG - range description URB - urban description WLH - wildlife description WOO - woodland description These descriptions are usually filed as hard copies in this subsection or stored in CAMPS with a reference sheet in this subsection. If used, the reference sheet should contain detailed instructions on retrieving the printouts from CAMPS. Section II-iii-A November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Use and Explanation of Cropland Interpretations Information in this subsection can be used to plan the use and management of soils for crops or pasture. Conservation planners and others using this information can evaluate the effect of crop management systems on productivity and on the environment in all or part of the county. This information can be used to maintain or create a land use pattern that is in harmony with the natural soil. This subsection contains the following: Explanation of Soil Erodibility (K) Factor Explanation of Soil-Loss Tolerance (T) Value Explanation of Wind Erodibility Group (I) Explanation of Hydrologic Soil Groups Prime Farmland List Land Capability Classification Crop Yield Estimates Section II-iii-A November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Soil Erodibility (K) Factor and Soil-loss Tolerance (T) Value General Soil erodibility factors (K) and soil-loss tolerances (T) are used in an equation that predicts the amount of soil loss resulting from rainfall erosion of cropland. The soil-loss prediction procedure is useful to guide the selection of practices for soil and water conservation. The procedure is outlined and illustrated in Agricultural Handbook No. 537. Soil Erodibility (K) Factor The soil erodibility factor "K" indicates the susceptibility of a soil to sheet and rill erosion by water. Soil properties that influence erodibility by water are: (1) Those that affect infiltration rate, movement of water through the soil, and water storage capacity; and (2) those that resist dispersion, splashing, abrasion, and transporting forces from rainfall and runoff. Soil properties that are most important are percent silt plus very fine sand, percent organic matter, percent sand coarser than very fine sand, structure, and permeability. Soil-loss Tolerance (T) Factor The soil-loss tolerance factor "T" is an estimate of the maximum annual rate of soil erosion that can occur over a sustained period without affecting crop productivity. The rate is expressed in tons of soil loss per acre per year. Rates of 1 through 5 are used, depending upon soil properties and prior erosion. Soil-loss tolerances were subjectively evaluated, based on the following general guides: 1. Maintenance of an adequate rooting depth for crop production. 2. Potential crop yield reduction. 3. Maintenance of water control structures affected by sedimentation. 4. Prevention of gullies. 5. Value of nutrients lost. Section II-iii-A November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Wind Erodibility Groups Soil erodibility by wind is directly related to the percentage of dry nonerodible surface soil aggregates larger than 0.84 mm in diameter. From this percentage, the wind erodibility index (I-factor) is determined. The I-factor is an expression of the stability of these soil aggregates against breakdown by tillage and abrasion from wind erosion. Soils are placed in Wind Erodibility Groups (WEG) having similar percentages of dry soil aggregates larger than 0.84 mm as shown in the following table. _________________________________________________________________ Dry Soil Wind Aggregates Erod. >0.84mm Index WEG Properties of Soil Surface Layer Percent T/Ac/Yr _________________________________________________________________ 1 Very fine sand, fine sand, sand, or coarse sand. 1 310 2 Loamy very fine sand, loamy fine sand, loamy 10 134 sand, loamy coarse sand, or sapric (1) organic soil materials. 3 Very fine sandy loam, fine sandy loam, sandy 25 86 loam, or coarse sandy loamy. 4 Clay, silty clay, noncalcareous clay loam, or 25 86 silty clay loam with >35 percent clay content. 4L Calcareous loam, silt loam, clay loam, or 25 86 silty clay loam. 5 Non calcareous loam and silt loam with <20 40 56 percent clay content, or sandy clay loam, sandy clay, and hemic (1) organic soil materials. 6 Noncalcareous loam and silt loam with >20 45 48 percent clay content, or noncalcareous clay loam with <35 percent clay content. 7 Silt, noncalcareous silty clay loam with 50 38 >35 percent clay content and fibric (1) organic soil material. 8 Soils not suitable for cultivation due to -- -- coarse fragments or wetness; wind erosion is not a problem. _________________________________________________________________ (1) See Soil Taxonomy for definition. Section II-iii-A November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Hydrologic Soil Groups General The Hydrologic Soil Group, designated A, B, C, or D, is a group of soils that, when saturated, have the same runoff potential under similar storm and cover conditions. Soil properties that influence runoff potential are those that influence the minimum rate of infiltration for a bare soil after prolonged wetting and when not frozen. These properties are depth to seasonally high water table, intake rate, and permeability after prolonged wetting, and depth to very slowly permeable layer. The influences of ground cover and slope are treated independently---not in hydrologic soil groups. In the definitions of the classes, infiltration rate is the rate at which water enters the soil at the surface and is controlled by surface conditions. Transmission rate is the rate at which water moves in the soil and is controlled by properties of the soil layers. Hydrologic Soil Group A Soils having high infiltration rates even when thoroughly wetted and consisting chiefly of deep, well-drained to excessively drained sands or gravels. These soils have a high rate of water transmission. (Low runoff potential) Hydrologic Soil Group B Soils having moderate infiltration rates when thoroughly wetted, consisting chiefly of moderately deep or deep, moderately well or well drained soils with moderately fine to moderately coarse textures. These soils have a moderate rate of water transmission. Hydrologic Soil Group C Soils having slow infiltration rates when thoroughly wetted, consisting chiefly of (1) soils with a layer that impedes the downward movement of water, or (2) soils with moderately fine or fine textures and slow infiltration rate. These soils have a slow rate of water transmission. Section II-iii-A November 1, 1995 Hydrologic Soil Group D Soils having very slow infiltration rates when thoroughly wetted, consisting chiefly of (1) clayey soils with high swelling capacity or potential, (2) soils with a high permanent water table, (3) soils with a claypan or clay layer at or near the surface, and (4) shallow soils over nearly impervious materials. These soil have a very slow rate of water transmission. (High runoff potential) Section II-iii-A November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Prime Farmland Prime farmland is land that has the best combination of physical and chemical characteristics for producing food, feed, forage, fiber, and oilseed crops, and is also available for these uses (the land could be cropland, pastureland, forest land, or other land, but not urban built-up land or water). It has the soil quality, growing season, and moisture supply needed to economically produce sustained high yields of crops when treated and managed, including water management, according to acceptable farming methods. In general, prime farmlands have an adequate and dependable water supply from precipitation or irrigation, a favorable temperature and growing season, acceptable acidity or alkalinity, acceptable salt content, and few or no rocks. They are permeable to water and air. Prime farmlands are not excessively erodible or saturated with water for a long period of time, and they either do not flood frequently or are protected from flooding. The following list of soil survey map units meet the soil requirements for prime farmland in LOWER NEW CASTLE COUNTY PROJECT, DELAWARE. Soils that have limitations, such as a high water table or flooding, may qualify as prime farmland if these limitations are overcome by such measures as drainage or flood control. In the following list, the measures needed to overcome the limitations of a map unit, if any, are shown in parenthesis after the map unit name. Section II-iii-A November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Unique Farmland Unique farmland is land other than prime farmland that is used for the production of specific high value food and fiber crops. It has the special combination of soil quality, location, growing season, and moisture supply needed to economically produce sustained high quality and/or high yields of a specific crop when treated and managed according to acceptable farming methods. Examples of such crops are citrus, tree nuts, olives, cranberries, fruit, and vegetables. Specific characteristics of unique farmland include: 1. Is used for a specific high-value food or fiber crop. 2. Has a moisture supply that is adequate for the specific crop. The supply is from stored moisture, precipitation, or a developed irrigation system. 3. Combines favorable factors of soil quality, growing season, temperature, humidity, air drainage, elevation, aspect, or other conditions, such as nearness to market, that favor the growth of a specific food or fiber crop. The following list of soil survey map units meet the requirements for unique farmland in LOWER NEW CASTLE COUNTY PROJECT, DELAWARE. Section II-iii-A November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Highly Erodible Land General The basis for identifying highly erodible land is the erodibility index of a soil map unit. The erodibility index of a soil is determined by dividing the potential erodibility for each soil by the soil loss tolerance (T) value established for the soil. The T value represents the maximum annual rate of soil erosion that could take place without causing a decline in long-term productivity. A soil map unit with an erodibility index of 8 or more is a highly erodible soil map unit. Water Erosion Potential erodibility for sheet and rill erosion is estimated by multiplying the following factors of the Universal Soil Loss Equation (USLE): 1. Rainfall and runoff factor (R) 2. Susceptibility of the soil to water erosion (K) 3. Combined effects of slope length and steepness (LS) The erodibility index for sheet and rill erosion is represented by the formula RKLS/T. A soil map unit is highly erodible if the LS factor for the shortest length and minimum percent of slope is used and the RKLS/T value equals or exceeds 8. A soil map unit is potentially highly erodible if: (1) the RKLS/T value using the minimum LS factor is less than 8 and (2) the RKLS/T value using the maximum LS factor is equal to or greater than 8. Wind Erosion Potential erodibility from wind erosion is estimated by multiplying the following factors of the Wind Erosion Equation (WEQ). 1. Climatic characterization of windspeed and surface soil moisture (C) 2. The susceptibility of the soil to wind erosion (I) Section II-iii-A November 1, 1995 The erodibility index for wind erosion is represented by the formula CI/T. A soil map unit is highly erodible if the CI/T value equals or exceeds 8. Section II-iii-A November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Land Capability Classification The land capability classification system is used to show, in a general way, the suitability of soils for cropland. It is a three-category interpretative system. The two highest categories, class and subclass, give broad perspective of the suitability of map units for certain crops or pasture. These categories indicate the degree and kinds of limitations for these uses. The system evaluates soils for mechanized farming systems that produce the more common cultivated field crops, such as corn, small grains, cotton, hay, and field grown vegetables. Capability Class The highest category of the system is the capability class. The capability classes are groups of soils that have the same general suitability for the broad kinds of use common on farms and ranches. There are eight classes designated by Roman numerals I through VIII. Classes I, II, III, and IV are suitable for mechanized production of common field crops if properly managed, and for production of pasture and woodland. The degree of limitation for production of cultivated crops increases progressively for class I to class IV. Limitations may affect production as well as the risk of permanent soil deterioration, as by erosion. Classes V, VI, and VII are generally not suited to mechanized production of common field crops without special management, but are suitable for permanent cover such as grasses and trees. The severity of the soil limitations for crops increases from class V to class VII. Areas in class VIII are generally not suitable for crops, pasture, or wood products without management that is impractical. Class VIII areas may have potential for other uses, such as recreation or wildlife habitat. Capability Subclass The subclass identifies the dominant kind of limitation in the class. They are designated by adding a small letter, e, w, s, or c, to the class numeral, for example, IIe. The letter e shows that the main limitation is risk of erosion unless a close-growing plant cover is maintained: w shows that water in or on the soil interferes with plant growth or cultivation (in some soils the wetness can be partly corrected by artificial drainage); s shows that the soil is limited mainly because it is Section II-iii-A November 1, 1995 shallow, droughty, or stony; and c, used in only some parts of the United States, shows that the chief limitation is climate that is very cold or very dry. There are no subclasses in class I because the soils of this class have few limitations. The soils in class V are subject to little or no erosion, but they have other limitations that restrict their use mainly to pasture, woodland, wildlife habitat, or recreation. Class V contains only the subclasses indicated by w, s, or c. Capability Unit The lowest category of the capability system is the capability unit. Capability units are soil groups within a subclass. The soils in a capability unit are enough alike to be suited to the same crops and pasture plants, to require similar management, and to have similar productivity. Units are designated by Arabic numerals, for example IIe-2. This category is not used in all soil surveys. The capability class and subclass for soil map units in LOWER NEW CASTLE COUNTY PROJECT, DELAWARE are in this section in the LAND CAPABILITY CLASSES AND YIELDS PER ACRE OF CROPLAND table. Section II-iii-A November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Crop Yield Estimates The average yields per acre that can be expected of the principal crops under a high level of management are presented in the following table. In any given year, yields may be higher or lower than those indicated in the table because of variations in rainfall and other climatic factors. The yields are based mainly on the experience and records of farmers, conservationists, and extension agents. Available yield data from nearby counties and results of field trials and demonstrations are also considered. The management needed to obtain the indicated yields of the various crops depends on the kind of soil and the crop. Management can include drainage, erosion control, and protection from flooding; the proper planting and seeding rates; suitable high-yielding crop varieties; appropriate and timely tillage; control of weeds, plant diseases, and harmful insects; favorable soil reaction and optimum levels of nitrogen, phosphorus, potassium, and trace elements for each crop; effective use of crop residue, barnyard manure, or green manure crops; and harvesting that insures the smallest possible loss. The estimated yields reflect the productive capacity of each soil for each of the principal crops. Yields are likely to increase as new production technology is developed. The productivity of a given soil compared with that of other soils, however, is not likely to change. Absence of a yield indicates that the soil is not suited to the crop or the crop is generally not grown on the soil. Section II-iii-C November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Forest Land Interpretations Woodland Ordination Symbol The ordination symbol has two parts: The class and subclass. Example: 9A CLASS SUBCLASS | | 9 A Ordination Class Symbol Productivity Class. The first element in ordination is a number that denotes potential productivity in terms of cubic meters of wood per hectare per year for an indicator tree species. The larger the number, the greater the potential productivity. Most woodland productivity values have been obtained from conversion of site index data. A mean annual increment of one cubic meter per hectare equals 14.3 cubic feet per acre (For quick conversion a factor of 15 may be used). Examples: 1 means 1 cubic meter per hectare per year (14.3 cu.ft./ac) 2 means 2 cubic meters per hectare per year (28.6 cu.ft./ac) 10 means 10 cubic meters per hectare per year (143 cu.ft./ac) Indicator Species. The indicator species is the species that is common in the area and is generally, but not necessarily, the most productive on the soil. It is the species that determines the ordination class. To make comparisons of productivity consult the "Woodland Productivity Table" which lists productivity for all species where data have been collected. Site Index. Site index is determined by taking height measurements and determining the age of selected trees within stands of a given species. This index is the average height, in feet, that the trees attain in a specified number of years. This index applies to fully stocked, even-aged, unmanaged stands. Site indexes shown in the woodland productivity table are averages based on measurements made at sites that are representative of the soil series and where the site has been free of past fire and disturbances. When comparing site index and woodland productivity of different soils, the values for the same tree species should be compared. Ordination Subclass Symbol Section II-iii-C November 1, 1995 The second element or subclass is indicated by a capital letter, which indicates certain soil or physiographic characteristics that contribute to important hazards or limitations in management. These are listed and defined on the following page. Ordination Subclass Definitions and Implications Subclass R (relief or slope steepness). Soil that have restrictions or limitations for forest land use or management because of steepness of slope. Subclass X (stoniness or rockiness). Soils that have restrictions or limitations for forest land use or management because of stones or rocks. Subclass W (excessive wetness). Soils in which excessive water, either seasonally or year round, causes significant limitations for forest land use and management. These soils may have restricted drainage, a high water table, or flooding hazard that adversely affects either stand development or management. Subclass T (toxic substances). Soils that have within the root zone excessive alkalinity, acidity, salt, or other toxic substances that limit or impede development of desirable species. Subclass D (restricted rooting depth). Soils that have restrictions or limitations for forest land use and management because of the rooting depth. For example, soils that are underlain by hard rock, hardpan, or other layers in the soil that restrict roots. Subclass C (clayey soils). Soils that have restrictions or limitations for forest land use or management because of the kind or amount of clay in the upper part of the soil profile. Subclass S (sandy soils). Dry, sandy soils that impose equipment limitations, have low moisture holding capacity, and normally are low in available plant nutrients. Subclass F (fragmental or skeletal soils). Soils that have restrictions or limitations for forest land or management because they contain large amounts of rock fragments Section II-iii-C November 1, 1995 that are larger than 2 mm and smaller than 10 inches. This subclass includes flaggy soils. Subclass A (no limitations or slight limitations). Soils that have no significant restrictions or limitations for forest land use or management. Multiple Limitations Some soils may have more than one limiting characteristic, but only one symbol will be used. Priority in placing each kind of soil into a subclass must be in the order in which the subclass characteristics are listed above. Plant competition and special considerations are not to be used to determine subclass. Section II-iii-C November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Woodland Management and Productivity This table presents information about management and productivity for each map unit in the survey area which is suitable for producing timber. Management concerns which are covered include hazard of erosion, equipment use, seedling mortality, and windthrow hazard. Ratings of SLIGHT, MODERATE, or SEVERE are used to indicate the degree of major soil limitations. Information on potential productivity includes plant competition, common trees, site index, productivity class, and trees to plant. Management Concerns Erosion Hazard. The risk of erosion is slight if the expected soil loss is small; moderate if some measures are needed to control erosion during logging; and severe if intensive management or special equipment and methods are needed to prevent excessive loss of soil. Equipment Limitation. A rating of slight indicates that use of equipment is not limited to a particular kind of equipment or time of year; moderate indicates a short seasonal limitation, or a need for some modification in management of equipment; and severe indicates a seasonal limitation, a need for special equipment or management, or a hazard in the use of equipment. Seedling Mortality. The ratings are for seedlings from a good planting stock that are properly planted during a period of sufficient rainfall. A rating of slight indicates that the expected mortality of the planted seedlings is less than 25 percent; moderate - 25 to 50 percent; and severe - more than 50 percent. Windthrow Hazard. A rating of slight indicates that trees in wooded areas are not expected to be blown down by commonly occurring winds; moderate - that some trees are blown down during periods of excessive soil wetness and strong winds; and severe - that many trees are blown down during periods of excessive soil wetness and moderate or strong winds. Potential Productivity Plant Competition. A rating of slight indicates little or no competition from other plants; moderate indicates that plant competition is expected to hinder the development of the fully stocked stand of desirable trees; and severe means that plant Section II-iii-C November 1, 1995 competition is expected to prevent the establishment of a desirable stand unless the site is intensively prepared, weeded, or otherwise managed for the control of undesirable plants. Common Trees. Trees which generally occur on the soil are listed regardless of economic importance. Site Index and Productivity Class. These are discussed under ordination class symbol. Trees to Plant. Trees that are suitable for commercial wood production and that are adapted to the soil. See the National Forestry Manual, Subpart B for criteria used in rating management concerns. Section II-iii-D November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Nonagricultural Interpretations General The purpose of these interpretative ratings is to help engineers, planners, and others understand how soil properties influence behavior when used for nonagricultural uses such as building site development or construction materials. Soils are rated for the uses expected to be important or potentially important to users of soil survey information. Ratings for proposed uses are given in terms of limitations and restrictive features; suitability and restrictive features; or only restrictive features. Only the most restrictive features are listed. Other features may need to be treated to overcome soil limitations for a specific purpose. Soils are rated in their "natural" state, that is, no unusual modification of the soil site or material is made other than that which is considered normal practice for the rated use. Even though soils may have limitations, it is important to remember that engineers and others can modify soil features or can design or adjust the plans for a structure to compensate for most degrees of limitations. Most of these practices, however are costly. The final decision in selecting a site for a particular use generally involves weighing the costs for site preparation and maintenance. Limitation Ratings 1. Slight - is the rating given soils that have properties favorable for the use. The degree of limitation is minor and can be overcome easily. Good performance and low maintenance can be expected. 2. Moderate - is the rating given soils that have properties moderately favorable for the use. This degree of limitation can be overcome or modified by special planning, design, or maintenance. During some part of the year, the expected performance is less desirable than for soils rated slight. 3. Severe - is the rating given soils that have one or more properties unfavorable for the rated use, such as steep slopes, bedrock near the surface, flooding, high shrink- swell potential, a seasonal high water table, or low strength. This degree of limitation generally requires major soil reclamation, special design, or intensive maintenance, which in most situations is difficult and costly. Section II-iii-D November 1, 1995 Suitability Ratings 1. Good - means the soil has properties favorable for the use. Good performance and low maintenance can be expected. 2. Fair - means the soil is moderately favorable for the use. One or more soil properties make these soils less desirable than those rated good. 3. Poor - means the soil has one or more properties unfavorable for the use. Overcoming the unfavorable property requires special design, extra maintenance, or costly alteration. Section II-iii-D November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Building Site Development General Soil properties influence development of building sites, including the selection of the site, the design of the structure, construction, performance after construction, and maintenance. Soil limitation ratings of slight, moderate, and severe are given for shallow excavations, dwellings with and without basements, small commercial buildings, local roads and streets, and lawns, landscaping, and golf fairways. Shallow Excavations Shallow excavations are trenches or holes dug in the soil to a maximum depth of 5 or 6 feet. They are used for pipelines, sewerlines, telephone and power transmission lines, basements, open ditches, and cemeteries. The excavations are most commonly made by trenching machines or backhoes. The ratings are based on the soil properties that influence ease of digging and resistance to sloughing. Dwellings With or Without Basements These are single-family houses of three stories or less. The foundation is assumed to be spread footings of reinforced concrete built on undisturbed soil at a depth of 2 feet or the depth of maximum frost penetration, whichever is deeper, for houses without basements, or at a depth of 7 feet if a basement is constructed. The ratings are based on properties affecting soil strength and settlement under a load, and those that affect excavation and construction costs. Small Commercial Buildings Limitation ratings are given for undisturbed soil on which small commercial buildings of less than three stories without basements are built. The foundation is assumed to be spread footings of reinforced concrete at a depth of 2 feet or the the depth of maximum frost penetration, whichever is deeper. Local Roads and Streets Limitation ratings are given for the use of soils for Section II-iii-D November 1, 1995 construction of improved local roads and streets that have all-weather surfacing, commonly of asphalt, gravel with binder in it, or concrete, and that are expected to carry automobile traffic all year. These roads and streets are graded to shed water, and conventional drainage measures are provided. With the probable exception of the hard surface, roads and streets are built mainly from the soil at hand. Lawns, Landscaping, and Golf Fairways The soils are rated for their use in establishing and maintaining turf for lawns and golf fairways and ornamental trees and shrubs for residential type landscaping. The ratings are based on the use of soil material at the location with some land smoothing. Irrigation may or may not be needed and is not a criterion in rating. Traps, trees, roughs, and greens are not considered as part of the golf fairway. The properties considered are those that affect plant growth and trafficability after vegetation is established. See the National Soil Handbook, Part 603, for criteria used in rating specific uses. Section II-iii-D November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Construction Material General Soils are rated as sources for roadfill, topsoil, sand, and gravel. Suitability ratings of good, fair, or poor are given for soils used as a source of roadfill and topsoil. Ratings of probable and improbable are given for sand and gravel. A rating of probable means that on the basis of the available evidence, the source material is likely to be in or below the soil. A rating of improbable means that the source material is unlikely to be in or below the soil. The ratings for sand and gravel do not consider the quality of the source material because quality depends on how the source material is to be used. Roadfill Roadfill consists of soil material that is excavated from its original position and used in road embankments elsewhere. The evaluations for roadfill are for low embankments that generally are less than 6 feet in height and are less exacting in design than high embankments such as those along superhighways. The rating is given for the whole soil, from the surface to a depth of about 5 feet, based on the assumption that soil horizons will be mixed in loading, dumping, and spreading. Soils are rated as to the amount of material available for excavation, the ease of excavation, and how well the material performs after it is in place. Sand Sand as a construction material is usually defined as particles ranging in size from 0.074 mm (sieve #200) to 4.75 mm (sieve #4) in diameter. Sand is used in great quantities in many kinds of construction. Specifications for each purpose vary widely. The intent of this rating is to show only the probability of finding material in suitable quantity. The suitability of the sand for specific purposes is not evaluated. If the lowest layer of the soil contains sand, the soil is rated as a probable source regardless of thickness. The assumption is that the sand layer below the depth of observation exceeds the minimum thickness. Gravel Gravel as a construction material is defined as particles ranging in size from 4.76 mm (sieve #4) to 76 mm (3 inches) in diameter. Section II-iii-D November 1, 1995 Gravel is used in great quantities in many kinds of construction. Specifications for each purpose vary widely. The intent of this rating is to show only the probability of finding material in suitable quantity. The suitability of the gravel for specific purposes is not evaluated. If the lowest layer of the soil contains gravel, the soil is rated as a probable source regardless of thickness. The assumption is that the gravel layer below the depth of observation exceeds the minimum thickness. Topsoil The term "topsoil" has several meanings. As used here, the term describes soil material used to cover an area so as to improve soil conditions for establishment and maintenance of adapted vegetation. Generally, the upper part of the soil, which is richest in organic matter, is most desirable; however, material excavated from deeper layers is also used. In this rating, the upper 40 inches of soil material is evaluated for use as topsoil. In the borrow area, the material below 40 inches is evaluated for its suitability for plant growth after the upper 40 inches is removed. The soil properties that are used to rate the soil as topsoil are those that affect plant growth, the ease of excavation, loading, and spreading, and those that affect the reclamation of the borrow area. See the National Soil Handbook, Part 603, for criteria used in rating specific uses. Section II-iii-E November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Recreational Interpretations General The purpose of these interpretative ratings is to help engineers, planners, and others understand how soil properties influence behavior when used for recreational uses such as camp areas, picnic areas, playgrounds, and paths and trails. Soils are rated for the uses expected to be important or potentially important to users of soil survey information. Ratings for proposed uses are given in terms of limitations. Only the most restrictive features are listed. Other features may need to be treated to overcome soil limitations for a specific purpose. Soils are rated in their "natural" state, that is, no unusual modification of the soil site or material is made other than that which is considered normal practice for the rated use. Even though soils may have limitations, it is important to remember that engineers and others can modify soil features or can design or adjust the plans for a recreational use to compensate for most degrees of limitations. Most of these practices, however are costly. The final decision in selecting a site for a particular use generally involves weighing the costs for site preparation and maintenance. Limitation Ratings 1. Slight - is the rating given soils that have properties favorable for the use. The degree of limitation is minor and can be overcome easily. Good performance and low maintenance can be expected. 2. Moderate - is the rating given soils that have properties moderately favorable for the use. This degree of limitation can be overcome or modified by special planning, design, or maintenance. During some part of the year, the expected performance is less desirable than for soils rated slight. 3. Severe - is the rating given soils that have one or more properties unfavorable for the rated use, such as steep slopes, bedrock near the surface, flooding, or a seasonal high water table. This degree of limitation generally requires major soil reclamation, special design, or intensive maintenance, which in most situations is difficult and costly. Section II-iii-E November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Recreational Development General The soils are rated according to limitations that affect their suitability for camp areas, picnic areas, playgrounds, and paths and trails. Not considered in these ratings, but important in evaluating a site, are location and accessibility of the area, size and shape of the area and its scenic quality, the ability of the soil to support vegetation, access to water, potential water impoundment sites available, and either access to public sewer lines or capacity of the soil to absorb septic tank effluent. Soils subject to flooding are limited in varying degrees for recreational use by the duration of flooding and the season when it occurs. Onsite assessment of height, duration, and frequency of flooding is essential in planning recreational facilities. Camp Areas These are tracts of land used intensively as sites for tents, trailers, campers, and accompanying activities of outdoor living. Camp areas require such site preparation as shaping and leveling in areas for tents and parking areas, for stabilizing roads and intensively used areas, and for installing sanitary facilities and utility lines. Camp areas are subject to heavy foot traffic and some vehicular traffic. The soils are rated on the basis of soil properties that influence the ease of developing camping area and the performance of the camping area after development. Soil properties that influence trafficability and promote the growth of vegetation after heavy use are also important. Picnic Areas Picnic areas are natural or landscaped tracts used primarily for preparing meals and eating outdoors. These areas are subject to heavy foot traffic. Most vehicular traffic is confined to access roads and parking lots. Soils are rated on the basis of properties that influence development costs of shaping the site, trafficability, and growth of vegetation after development. The surface of picnic areas should absorb rainfall readily, remain firm under heavy foot traffic, and not be dusty when dry. Playgrounds These are areas used intensively for games such as baseball, Section II-iii-E November 1, 1995 football, and similar activities. Playgrounds require a nearly level soil that is free of stones and that can withstand heavy foot traffic and still maintain adequate vegetation. Soils are rated on the basis of properties that influence cost of shaping, trafficability, and growth of vegetation. Slope and stoniness are the main concerns in developing playgrounds. For good trafficability, the surface of playgrounds should absorb rainfall readily, remain firm under heavy foot traffic, and not be dusty when dry. Paths and Trails Paths and trails are used for walking, horseback riding, and similar uses, and should require little or no cutting and filling in site preparation. Soils are rated on properties that influence trafficability and erodibility. Paths and trails should remain firm under foot traffic and not be dusty when dry. See the National Soils Handbook, Part 603, for criteria used in rating specific uses. Section II-iii-F November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Wildlife Interpretations General Soils directly affect the kind and amount of vegetation that is available to wildlife as food and cover. They also affect the development of water impoundments. The kind and abundance of wildlife that populate an area depend largely on the amount and distribution of food, cover, water, and living space. If any one of these elements is missing, inadequate, or inaccessible, wildlife will be scarce or will not inhabit the area. If the soils have the potential, wildlife habitat can be created or improved by planting appropriate vegetation, properly managing the existing plant cover, and fostering the natural establishment of desirable plants. Soils are rated according to their potential for providing habitat for various kinds of wildlife. This information can be used in planning parks, wildlife refuges, nature study areas, and other developments for wildlife. It can also be used in selecting soils that are suitable for establishing, improving, or maintaining specific elements of wildlife habitat. Suitability Ratings Good - means that the element of wildlife habitat or the kind of habitat is easily created, improved, or maintained. Few or no limitations affect management, and satisfactory results can be expected if the soil is used for the designated purpose. Fair - means that the element of wildlife habitat or kind of habitat can be created, improved, or maintained in most places. Moderately intensive management is required for satisfactory results. Poor - means that limitations are severe for the designated element or kind of wildlife habitat. Habitat can be created, improved, or maintained in most places, but management is difficult and requires intensive effort. Section II-iii-F November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Wildlife Habitat Suitability Description of Wildlife Habitat Elements Grain and seed crops are seed-producing annuals used by wildlife. Examples are corn, wheat, rye, oats, barley, millet, buckwheat, and sunflowers. Grasses and legumes are domestic perennial grasses and herbaceous legumes that are planted for wildlife food and cover. Examples are fescue, bluegrass, bromegrass, timothy, orchardgrass, clover, alfalfa, trefoil, reed canarygrass, and crownvetch. Wild herbaceous plants are native and naturally established herbaceous grasses and forbs, including weeds, that provide food and cover for wildlife. Examples are bluestem, indiangrass, blueberry, goldenrod, lambsquarters, dandelions, blackberry, ragweed, wheatgrass, fescue, and nightshade. Hardwood trees and the associated woody understory provide cover for wildlife and produce nuts or other fruit, buds, catkins, twigs, bark, or foliage that wildlife eat. Examples of native plants are oak, poplar, cherry, apple, birch, beech, maple, hickory, hazelnut, black walnut, and viburnum. Examples of fruit-bearing shrubs that are commercially available and suitable for planting on soils rated good are hawthorn, honeysuckle, sumac, silky dogwood, highbush cranberry, autumn olive, and crabapple. Coniferous plants are cone-bearing trees, shrubs, or ground cover that furnish habitat or supply food in the form of browse, seed, or fruitlike cones. Examples are pine, spruce, hemlock, fir, yew, cedar, larch, and juniper. Wetland plants are annual and perennial wild herbaceous plants that grow on moist or wet sites, exclusive of submerged or floating aquatics. They produce food or cover for wildlife that use wetland as habitat. Examples of wetland plants are smartweed, wild millet, rushes, sedges, reeds, wildrice, arrowhead, waterplantain, pickerelweed, and cattail. Shallow water are bodies of surface water that have an average depth of less that 5 feet and are useful as habitat for wildlife. They can be naturally wet areas, or they can be created by dams or levees, or by water-control devices in marshes or streams. Examples are muskrat marshes, waterfowl feeding areas, wildlife watering developments, beaver ponds, and other wildlife ponds. Section II-iii-F November 1, 1995 Kinds of Wildlife Habitat Openland habitat consists of croplands, pastures, meadows, and areas that are overgrown with grasses, herbs, shrubs, and vines. These areas produce grain and seed crops, grasses and legumes, and wild herbaceous plants. The kind of wildlife attracted to these areas include bobwhite quail, pheasant, meadowlark, field sparrow, killdeer, cottontail rabbit, red fox, and woodchuck. Woodland habitat consists of hardwood or conifers, or a mixture of these and associated grasses, legumes and wild herbaceous plants. Examples of wildlife attracted to this habitat are wild turkey, woodcock, thrushes, woodpeckers, owl, tree squirrels, gray fox, porcupine, raccoon, deer, and black bear. Wetland habitat consists of water-tolerant plants in open, marshy or swampy, shallow water areas. Examples of wildlife attracted to this habitat are ducks, geese, herons, bitterns, rails, kingfishers, muskrat, otter, mink, and beaver. Section II-iii-G November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Pasture and Hayland Interpretations This subsection provides information concerning the suitability of soils for the production of pasture and hayland. This subsection may contain pasture and hayland suitability groupings, land capability and yield estimates, yield estimates for individual grasses or legumes, or other information pertaining to the production of forage. Pasture and Hayland Suitability Groupings Soils are placed in pasture and hayland groups according to their suitability for the production of forage. The soils in each group are enough alike to be suited to the same grasses or legumes, to have similar limitations and hazards, to require similar management, and to have similar productivity and other responses to management. Thus, the pasture and hayland suitability group is a convenient way of grouping the soils for their management. If used, these groupings are identified and described in this subsection. Yield Estimates The average yields per acre that can be expected of the principal pasture or hayland crops, under a high level of management, are presented in this subsection. In any given year, yields may be higher or lower than those indicated in the tables because of variations in rainfall or other climatic factors. The yields are based mainly on the experience and records of farmers, conservationists, and extension agents. Available yield data from nearby counties and results of field trials and demonstrations are also considered. Under good management, proper grazing is essential for the production of high quality forage, stand survival, and erosion control. Proper grazing helps plants maintain sufficient and generally vigorous top growth during the growing season. Brush control is essential in many areas, and weed control generally is needed. Rotation grazing and renovation are also important management practices. Yield estimates are often provided in animal unit months (AUM) or the amount of forage or feed required to feed one animal unit (one cow, one horse, one mule, five sheep, or 5 goats) for 30 days. Section II-iii-I November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Windbreak Interpretations Windbreaks protect livestock, buildings, and yards from wind and snow. They also protect fruit trees and gardens, and they furnish habitat for wildlife. Several rows of low-growing and high-growing broadleaf and coniferous trees and shrubs provide the most protection. Field windbreaks are narrow plantings made at right angles to the prevailing wind and at specific intervals across the field. The interval depends on the erodibility of the soil. Field windbreaks protect cropland and crops from wind, help to keep snow on the fields, and provide food and cover for wildlife. Windbreaks are often planted on land that did not grow trees originally. Knowledge of how trees perform on such land can be gained only by observing and recording their performance where trees have been planted and survived. The problem is compounded by the fact that many favorite windbreak species are not indigenous to the areas in which they are planted. Each tree or shrub species has certain climatic and physiographic limits. Within these parameters a tree or shrub may be well or poorly suited because of soil characteristics. Each tree or shrub also has definable potentials of height growth depending on the factors just mentioned. Accurate definitions of potential heights are necessary for proper windbreak planning and design. Information in this subsection, which includes windbreak suitability groups and a windbreak and environmental plantings table, can be used as a guide in planning windbreaks and screens. See part 537 of the National Forestry Manual for additional information. Section II-iii-J November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Engineering Interpretations Soil properties relating to engineering interpretations are determined by field examination of the soils and by laboratory index testing of some benchmark soils. Established standard procedures are followed. During the survey, many shallow borings are made and examined to identify and classify the soils and to delineate them on the soil maps. Samples are taken from some typical profiles and tested in the laboratory to determine grain-size distribution, plasticity, and compaction characteristics. Estimates of soil properties are based on field examinations, on laboratory tests of samples from the survey area, and on laboratory tests of samples of similar soils in nearby areas. Tests verify field observations, verify properties that cannot be estimated accurately by field observation, and help characterize key soils. Pertinent soil and water features also are provided in this section. Tables in this subsection include the following: **Engineering Index Properties **Physical and Chemical Properties **Water Features **Soil Features **Water Management Section II-iii-J November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Engineering Index Properties General This table gives estimates of the engineering classification and of the range of index properties for the major layers of each soil in the survey areas. Most soils have layers of contrasting properties within the upper 5 to 6 feet. Information in this table includes depth, USDA texture, Unified and AASHTO Classification, rock fragments larger than 3 inches, percentage passing designated sieves, liquid limit, and plasticity index. Properties Depth to the upper and lower boundaries of each layer is indicated. Texture is given in the standard terms used by the USDA. The terms are defined according to percentages of sand, silt, and clay in the fraction of the soil that is less than 2 millimeters in diameter. (Textural terms are defined in Chapter 4, Soil Survey Manual or in the glossary of most soil survey reports) If the content of particles coarser than sand is 15 percent or more, an appropriate modifier is added, for example , "gravelly". Unified classification system classifies soils according to properties that affect their use as construction material. Soils are classified according to grain-size distribution of the fraction less than 3 inches in diameter and according to plasticity index, liquid limit, and organic matter content. AASHTO classification is the system adopted by the American Association of State Highway and Transportation Officials. It classifies soils according to those properties that affect roadway construction. Rock fragments, 3 to 10 inches and greater than 10 inches in diameter, are indicated as a percentage of the total soil in on a dry-weight basis. The percentages are estimates determined mainly by converting volume percentage in the field to weight percentage. Percentage (of soil particles) passing designated sieves is the percentage of the soil fraction less than 3 inches in diameter based on an ovendry weight. The sieves, numbers 4, 10, 40, and 200, have openings of 4.76, 2.00, 0.420, and 0.074 millimeters, respectively. Estimates are based on laboratory tests of soils Section II-iii-J November 1, 1995 sampled in the survey area and in nearby areas and on estimates made in the field. Liquid limit and plasticity index (Atterbery limits) indicate the plasticity characteristics of a soil. The estimates are based on test data from the survey area, or from nearby areas, and on field examination. Section II-iii-J November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Physical and Chemical Properties General This table shows estimates of some characteristics and features that affect soil behavior. These estimates are given for the major layers of each soil in the survey area. The estimates are based on field observations and on test data for these and similar soils. Information in this table includes depth, percent clay, moist bulk density, permeability, available water capacity, soil reaction, salinity, shrink-swell potential, K and T erosion factors, wind erodibility group, and percent organic matter. Properties Depth to the upper and lower boundaries of each layer is indicated. Clay (percent) as a soil separate, or component, consists of mineral soil particles that are less than 0.002 millimeter in diameter. The estimated clay content of each major soil layer is given as a percentage, by weight, of the soil material that is less than 2 millimeters in diameter. Moist bulk density is the weight of soil (ovendry) per unit volume. Volume is measured when the soil is at field moisture capacity, that is, the moisture content at 1/3 bar moisture tension. Weight is determined after drying the soil at 105 degrees C. The estimated moist bulk density of each major soil horizon is expressed in grams per cubic centimeter of soil material that is less than 2 millimeters in diameter. Permeability refers to the ability of a soil to transmit water or air. The estimates indicate the rate of movement of water through the soil when the soil is saturated. They are based on soil characteristics observed in the field, particularly structure, porosity, and texture. Available water capacity refers to the quantity of water that the soil is capable of storing for use by plants. The capacity for water storage in each major soil layer is stated in inches of water per inch of soil. The capacity varies, depending on soil properties that affect the retention of water and the depth of the root zone. Soil reaction is a measure of acidity or alkalinity and is expressed as a range in pH values. The range in pH of each major Section II-iii-J November 1, 1995 horizon is based on many field tests. For many soils, values have been verified by laboratory. Salinity is a measure of soluble salts in the soil at saturation. It is expressed as the electrical conductivity of the saturation extract, in millimhos per centimeter at 25 degrees C. Estimates are based on field and laboratory measurements at typical sites of nonirrigated soils. Shrink-swell potential is the potential for volume change in a soil with a loss or gain in moisture. Volume change occurs mainly because of the interaction of clay minerals with water and varies with the amount and type of clay minerals in the soil. Erosion factor K indicates the susceptibility of a soil to sheet and rill erosion by water (See Section II-iii-A, Cropland Interpretations). Erosion factor T is an estimate of the maximum average annual rate of soil erosion that can occur over a sustained period without affecting crop productivity. The rate is expressed in tons per acre per year (See Section II-iii-A, Cropland Interpretations). Organic matter is the plant and animal residue in the soil at various stages of decomposition. Section II-iii-J November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Water Features This table gives estimates of several important water features, which are used in land use planning that involves engineering considerations. Water features which are covered include hydrologic soil groups, flooding frequency and duration, and seasonal high water table. Hydrologic Soil Groups Soils with the same runoff potential are grouped into one of four Hydrologic Soil Groups. These groupings are used to estimate runoff from precipitation. Soils are assigned to one of four groups (See Section II-iii-A, Cropland Interpretations for a detailed explanation of hydrologic soil groups). Flooding The temporary covering of the soil surface by flowing water, is caused by overflowing streams, by runoff from adjacent slopes, or by inflow from high tides. Shallow water standing or flowing for short periods after rainfall or snowmelt is not considered flooding. Standing water in marshes and swamps or in a closed depression is considered ponding. Frequency, duration, and probable dates of occurrence are estimated. Frequency generally is expressed as none, occasional, or frequent. None means that flooding is not probable. Occasional means that flooding occurs infrequently under normal weather conditions (there is a 5 to 50 percent chance of flooding in any year). Frequent means that flooding occurs often under normal weather conditions (there is a 50 percent chance of flooding in any year). Common groups frequent and occasional flooding into one class. Duration is expressed as very brief (less than 2 days), brief (2 to 7 days), long (7 to 30 days), and very long (more than 30 days). Probable dates of occurrence that floods are most likely to occur are expressed in months. About two-thirds to three-fourths of all flooding occurs during the stated period. High Water Table (Seasonal) Section II-iii-J November 1, 1995 This is a zone of saturation at the highest average depth during the wettest season. It is at least 6 inches thick, persists in the soil for more than a few weeks, and is within 6 feet of the soil surface. The depth to a seasonal high water table applies to undrained soils. Soils that have a seasonal high water table are classified according to depth to the water table, kind of water table, and time of year when the water table is highest. Three kinds of seasonal high water table are recognized within the soil: apparent, perched, and artesian. Another kind is above the soil surface much of the time causing ponding. Apparent water table is the level at which water stands in a freshly dug, unlined borehole after adequate time for adjustments in the surrounding soil. Perched water table is one that exists in the soil above an unsaturated zone. A water table may be inferred to be perched on the basis of general knowledge of the area. To prove that a water table is perched, the water levels in boreholes must be observed to fall when the borehole is extended. Artesian water table is one that exists under hydrostatic head beneath an impermeable layer; when the impermeable layer has been penetrated by a cased borehole, the water rises. Ponding is standing water in a closed depression. The water is removed only by percolation, transpiration, or evaporation. November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Section II-iii-J Soil Features This table gives estimates of several important soil features which are used in land use planning that involves engineering considerations. Soil features which are covered include bedrock depth and hardness, cemented pan depth and hardness, subsidence, potential frost action, and risk of corrosion for uncoated steel or for concrete. Depth to Bedrock This value is given if bedrock is with a depth of 60 inches. The depth is based on many soil borings and observations made during soil mapping. The rock is specified as either soft or hard. If the rock is soft, excavations can be made with trenching machines, backhoes, or small rippers. If the rock is hard or massive, blasting or special equipment generally is needed for excavation. Cemented Pan Cemented pan is a nearly continuous layer of indurated or strongly cemented material having a hard, brittle consistency because the particles are are held together by cementing substances such as, calcium carbonate, or oxides of silicon, iron, or aluminum. These layers are identified when they occur within a depth of 60 inches. Pans are classified as "thin" or "thick". "Thin" cemented pans are thin enough so that excavations can be made with trenching machines, backhoes, or small rippers and other equipment common to construction of pipelines, sewerlines, cemeteries, and the like. "Thick" cemented pans are sufficiently thick or massive to require blasting or special equipment beyond which is considered normal in excavating for this type of construction. Subsidence Subsidence potential is the maximum possible loss of surface elevation from the drainage of wet soils having organic layers or semifluid mineral layers. Estimates of the depth of subsidence (in inches) that takes place soon after drainage (initial subsidence) and after oxidation (total subsidence) are given for soils that are likely to subside. November 1, 1995 Potential Frost Action This is the likelihood of upward or lateral movement of soil by the formation of segregated ice lenses (frost heave) and the subsequent loss of soil strength upon thawing. The following classes are used in regions where frost action is a potential problem: (1) Low -- soils are rarely susceptible to the formation of ice lenses, (2) Moderate -- soils are susceptible to the formation of ice lenses, resulting in frost heave and subsequent loss of soil strength, and (3) High -- soils are highly susceptible to the formation of ice lenses, resulting in frost heave and subsequent loss of soil strength. Risk of Corrosion Various metals and other materials corrode when on or in the soil, and some metals and materials corrode more rapidly when in contact with specific soils than when in contact with others. Corrosivity ratings are given for two of the common structural materials, uncoated steel and concrete. The risk of corrosion classes are low, moderate, and high. See Table 603-7 or Table 603-8 in part 603 of the National Soils Handbook for guides for estimating risk of corrosion for uncoated steel or concrete. Section II-iii-J November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Water Management Interpretations of soils for water management are given as limitations for pond reservoir areas; embankments, dikes, and levees; excavated pond (aquifer-fed); and as restrictive features that affect drainage, irrigation, terraces and diversions, and grassed waterways. Pond reservoir area is the area that holds water behind a dam or embankment. Soils best suited to this use have a low seepage potential, which is determined by the permeability and depth to fractured or permeable bedrock, or other permeable material. Embankments, dikes, and levees are raised structures of soil material constructed to impound water or protect land against overflow. They generally are less than 20 feet high and are constructed of "homogeneous" soil material (without a core zone) and compacted to medium density. Excavated ponds (aquifer-fed) are bodies of water created by excavating a pit or dugout into a ground-water aquifer. Excluded are ponds which are fed by surface runoff or that have embankments that impound water 3 feet or more above the original surface. Drainage is the process of removing excess surface and subsurface water from agricultural land. Soil features are listed that affect grading, excavation, and stability of trench sides or ditchbanks. Features are also listed which might affect productivity after drainage is installed. The availability of drainage outlets must also be considered. Irrigation is the controlled application of water to supplement rainfall for supporting plant growth. Soil features are listed that affect design, layout, construction, management, or performance of an irrigation system. Terraces and diversions are embankments or a combination of an embankment and a channel constructed across a slope to control erosion by diverting or storing surface runoff instead of permitting it to flow uninterrupted down the slope. Soil features are listed that affect the construction of terraces and diversions and that may cause problems after construction. Grassed waterways are natural or constructed channels that generally are broad and shallow and are covered with erosion-resistant grasses. They are used to conduct surface water to outlets at a nonerosive velocity. Soil features are Section II-iii-J November 1, 1995 listed that affect the construction and maintenance of the waterway, and also that affect the growth of grass after construction. See the National Soil Handbook, Part 603, for criteria used in rating specific uses. Section II-iii-K November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Waste Disposal Interpretations Sanitary Facilities The nature of the soil is important in selecting sites for sanitary facilities (such as septic tank absorption fields, sewage lagoons and sanitary landfills) and identifying limiting soil properties and site features to be considered in planning, design, and installation. The sanitary facilities table, with accompanying explanation, in this subsection can be used as a guide in developing sanitary facilities. Waste Management The nature of the soil is also important in the application of organic wastes and wastewater to land as fertilizers and irrigation; it is also important when the soil is used as a medium for treatment and disposal of these wastes. Favorable soil properties are required to prevent environmental damage. The use of organic wastes and wastewater as production resources will result in energy conservation, prevent the waste of these important resources, and prevent problems associated with their disposal. Where disposal is the goal, and a maximum amount is disposed in a minimum area to hold costs to a minimum, risk of environmental damage is the principal constraint. Where the reuse goal is pursued, and a minimum amount is applied to a maximum area to obtain the greatest benefit, environmental damage is unlikely. Interpretations developed for waste management may include ratings for (1) manure and food processing wastes; (2) municipal sewage sludge; (3)irrigation use of wastewater; or (4) treatment of wastewater by the slow rate process, overland flow process, or rapid infiltration process. If available, these should be located in this subsection. See the National Soil Handbook, Part 603, for criteria used in rating soils for sanitary facilities and waste management. Section II-iii-K November 1, 1995 LOWER NEW CASTLE COUNTY PROJECT, DELAWARE Sanitary Facilities The nature of the soil is important is selecting sites for sanitary facilities, and in identifying limiting soil properties and site features to be considered in planning, design, and installation. Soil limitations ratings of slight, moderate, or severe are given for septic tank absorption fields, sewage lagoons, and trench and area type sanitary landfills. Soil suitability ratings of good, fair, and poor are given for daily cover for landfills. Limitations or suitability terms used in this subsection are as follows: Slight (or Good) - relatively free of limitations or limitations are easily overcome. Moderate (or Fair) - limitations need to be recognized, but usually can be overcome with good management or special design. Severe (or Poor or Very Poor) - limitations are difficult or impractical to overcome. Sanitary Facility Type Septic Tank Absorption Fields are subsurface systems of tile or perforated pipe that distribute effluent from a septic tank into the natural soil. The centerline depth of the tile is assumed to be at a depth of 24 inches. Only the soil between depths of 24 and 60 inches is considered in making the ratings. The soil properties and site features considered are those that affect the absorption of the effluent, those that affect the construction and maintenance of the system, and those that may affect public health. Sewage Lagoons are shallow ponds constructed to hold sewage while aerobic bacteria decompose the solid and liquid wastes. Lagoons have a nearly level floor surrounded by cut slopes or embankments of compacted, relatively impervious soil material. Aerobic lagoons generally are designed so that the depth of sewage is 2 to 5 feet. Relatively impervious soil for the lagoon floor and sides is desirable to minimize seepage and contamination of local ground water. Sanitary Landfill (trench) is a method of disposing of solid waste by placing refuse in successive layers in an excavated trench. The waste is spread, compacted, and covered daily with a thin layer of soil that is excavated from the trench. When the trench is full, a final cover of soil material at least 2 feet Section II-iii-K November 1, 1995 thick is placed over the landfill. Properties that influence risk of pollution, ease of excavation, trafficability, and revegetation are major considerations. Sanitary Landfill (area) is a method of disposing of solid waste by placing refuse in successive layers on the surface of the soil. The waste is spread, compacted, and covered daily with a thin layer of soil that is imported from a source away from the site. A final cover of soil at least 2 feet thick is placed over the completed landfill. Properties that influence trafficability, revegetation, and risk of pollution are the main considerations for area type sanitary landfills. Daily Cover For Landfill is the soil material that is applied daily to compacted solid waste in an area type sanitary landfill. The cover material is obtained offsite, transported, and spread on the area. Suitability of a soil for use as cover is based on properties that reflect workability and the ease of digging and of moving and spreading the material over the refuse daily during both wet and dry periods. See the National Soil Handbook, Part 603, for criteria used in rating specific uses.