General Soil Map

The general soil map shows the survey area divided into groups of associated soils called general soil map units.This map is useful in planning the use and management of large areas.

To find information about your area of interest, locate that area on the map, identify the name of the map unit inthe area on the color-coded map legend, then refer to the section General Soil Map Units for a generaldescription of the soils in your area.

Detailed Soil Maps

The detailed soil maps can be useful in planning the use and management of small areas.

To find information about your area of interest, you can locate that area on the Index to Map Sheets. Go to theWeb Soil Survey for more information (http://websoilsurvey.nrcs.usda.gov/app/)

Note the map unit symbols that are in that area. Go to the Contents, which lists the map units by symbol andname and shows the page where each map unit is described. See the Contents for sections of this publicationthat may address your specific needs.

How to Use This Soil Survey

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This soil survey is a publication of the National Cooperative Soil Survey, a jointeffort of the United States Department of Agriculture and other Federal agencies,State agencies including the Agricultural Experiment Stations, and local agencies.The Natural Resources Conservation Service (formerly the Soil ConservationService) has leadership for the Federal part of the National Cooperative Soil Survey.

Major fieldwork for this soil survey was completed in 2000. Soil names anddescriptions were approved in 2001. Unless otherwise indicated, statements in thispublication refer to conditions in the survey area in 2000. This survey was madecooperatively by the Natural Resources Conservation Service; the United StatesDepartment of the Interior, Bureau of Land Management; the University of Idaho,College of Agriculture; and the Idaho Soil Conservation Commission. The survey ispart of the technical assistance furnished to the Boundary Soil Conservation District.

The most current official data are available through the NRCS Soil Data Martwebsite at http://soildatamart.nrcs.usda.gov. Soil maps in this survey may be copiedwithout permission. Enlargement of these maps, however, could causemisunderstanding of the detail of mapping. If enlarged, maps do not show the smallareas of contrasting soils that could have been shown at a larger scale.

The United States Department of Agriculture (USDA) prohibits discrimination in allof its programs on the basis of race, color, national origin, gender, religion, age,disability, political beliefs, sexual orientation, and marital or family status. (Not allprohibited bases apply to all programs.) Persons with disabilities who requirealternative means for communication of program information (Braille, large print,audiotape, etc.) should contact the USDA’s TARGET Center at 202-720-2600 (voiceor TDD).

To file a complaint of discrimination, write USDA, Director, Office of Civil Rights,Room 326W, Whitten Building, 14th and Independence Avenue SW, Washington, DC20250-9410, or call 202-720-5964 (voice or TDD). USDA is an equal opportunityprovider and employer.

Cover: Left—Schnoorson silt loam, protected, drained, 0 to 2 percent slopes, in foreground usedfor canola and wheat production. Rock outcrop-McArthur, very stony complex, 65 to 100 percentslopes, in background used for timber production and wildlife habitat. Center—Schnoorson siltloam, protected, drained, 0 to 2 percent slopes, in foreground used for wheat production. Caboose-Wishbone complex, 15 to 35 percent slopes, in middle ground used for timber production andpasture. Dufort-Rock outcrop-Kriest complex, 35 to 65 percent slopes, in background used fortimber production and wildlife habitat. Right—Pend Oreille ashy silt loam, 35 to 65 percent slopes,used for timber production and wildlife habitat.

Additional information about the Nation’s natural resources is available onlinefrom the Natural Resources Conservation Service at http://www.nrcs.usda.gov.

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Contents

Issued 2005

Part I

How to Use This Soil Survey ................................... iAlphabetical Index to Map Units .......................... viiSummary of Tables ................................................. xForeword ...............................................................xiiiGeneral Nature of the Survey Area............................ 2

History and Development ...................................... 2Geology ................................................................ 2Natural Resources ................................................ 3Agriculture ............................................................ 4Climate ................................................................. 4

How This Survey Was Made ...................................... 5Formation and Classification of the Soils ............. 9

Formation of the Soils ........................................... 9Parent Material ................................................. 9Climate ........................................................... 10Topography ..................................................... 10Living Organisms............................................ 11Time ............................................................... 11

Classification of the Soils ................................... 12Soil Series and Their Morphology ....................... 12General Soil Map Units ......................................... 73Detailed Map Units ................................................ 77References ........................................................... 131Glossary .............................................................. 133

Part II

How to Use This Soil Survey ................................... iDetailed Soil Map Unit Legend .............................. iv

Summary of Tables ................................................ viAgronomy ................................................................ 5

Crops and Pasture ................................................ 5Yields per Acre ................................................. 6

Land Capability Classification ............................... 7Prime Farmland .................................................... 8

Grazingland ........................................................... 23Woodland Understory Vegetation ........................ 23Grazingland Vegetation ....................................... 23Woodland Grazing .............................................. 24

Forestland ............................................................. 51Forestland Management and Productivity ........... 51Forestland in the Boundary County Area ............. 53

Recreation ........................................................... 119Recreation in the Boundary County Area .......... 120

Wildlife Habitat .................................................... 141Wildlife of the Boundary County Area................ 142

Engineering ......................................................... 153Building Site Development ................................ 153Sanitary Facilities ............................................. 155Agricultural Waste Management ........................ 156Construction Materials ...................................... 158Water Management ........................................... 159

Soil Properties .................................................... 299Engineering Index Properties ............................ 299Physical Properties .......................................... 300Chemical Properties ......................................... 301Water Features ................................................. 302Soil Features .................................................... 303

References ........................................................... 439Glossary .............................................................. 441

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Detailed Soil Map Unit Legend

103—Artnoc silt loam, 35 to 75 percent slopes104—Baldeagle gravelly medial silt loam, 35 to 75

percent slopes105—Bane loamy fine sand, 2 to 8 percent slopes102—Caboose-Wishbone complex, 15 to 35

percent slopes106—Caribouridge ashy silt loam, 0 to 15 percent

slopes107—Caribouridge ashy silt loam, 15 to 35 percent

slopes108—Caribouridge ashy silt loam, 35 to 65 percent

slopes109—Caribouridge, warm-Rock outcrop complex,

15 to 35 percent slopes113—Caribouridge, warm-Rock outcrop complex,

35 to 65 percent slopes110—Crash silt loam, 35 to 75 percent slopes112—Crash-Artnoc complex, 35 to 75 percent

slopes115—DeVoignes mucky silt loam, protected,

drained, 0 to 1 percent slopes117—Dodgecreek ashy silt loam, 2 to 12 percent

slopes120—Dufort ashy silt loam, 5 to 15 percent slopes116—Dufort ashy silt loam, 15 to 35 percent slopes114—Dufort ashy silt loam, 35 to 65 percent slopes191—Dufort-Rock outcrop-Kriest complex, 15 to 35

percent slopes101—Dufort-Rock outcrop-Kriest complex, 35 to 65

percent slopes134—Elmira loamy fine sand, 15 to 35 percent

slopes118—Farnhamton silt loam, protected, drained,

2 to 5 percent slopes141—Farnhamton silt loam, unprotected, drained,

0 to 4 percent slopes119—Farnhamton silt loam, unprotected,

undrained, 0 to 4 percent slopes189—Flemingcreek silt loam, 35 to 65 percent

slopes140—Frycanyon ashy silt loam, 2 to 8 percent

slopes

139—Highfalls gravelly ashy silt loam, 15 to 35percent slopes

196—Highfalls gravelly ashy silt loam, 35 to 65percent slopes

122—Highfalls stony ashy silt loam, 35 to 65percent slopes, bouldery

125—Idamont ashy silt loam, 5 to 15 percentslopes

126—Idamont ashy silt loam, 15 to 35 percentslopes

127—Idamont ashy silt loam, 35 to 65 percentslopes

123—Jaypeak gravelly ashy silt loam, 35 to 75percent slopes

121—Katka, very bouldery-Rock outcrop complex,35 to 65 percent slopes

124—McArthur, very stony-Rock outcrop complex,35 to 75 percent slopes

128—Myrtlecreek ashy sandy loam, 15 to 35percent slopes

129—Myrtlecreek ashy sandy loam, 35 to 75percent slopes

131—Pearsoncreek ashy loam, 15 to 35 percentslopes

132—Pearsoncreek ashy silt loam, 35 to 65percent slopes

133—Pearsoncreek-Rock outcrop complex, 15 to35 percent slopes

135—Pend Oreille ashy silt loam, 5 to 15 percentslopes

136—Pend Oreille ashy silt loam, 15 to 35 percentslopes

137—Pend Oreille ashy silt loam, 35 to 65 percentslopes

138—Pend Oreille-Rock outcrop complex, 15 to 35percent slopes

197—Pend Oreille-Stien, moist complex, 2 to 8percent slopes

146—Porthill silt loam, 2 to 8 percent slopes147—Porthill silt loam, 8 to 15 percent slopes150—Pywell muck, protected, drained, 0 to 1

percent slopes

v

201—Pywell muck, unprotected, undrained, 0 to 1percent slopes

151—Pywell-DeVoignes complex, 0 to 1 percentslopes

200—Pywell-DeVoignes complex, partially drained,0 to 2 percent slopes

154—Redraven medial silt loam, 15 to 35 percentslopes

155—Redraven medial silt loam, 35 to 65 percentslopes, bouldery

156—Ritz silt loam, protected, drained, 0 to 2percent slopes

142—Ritz silt loam, unprotected, undrained, 0 to 2percent slopes

143—Ritz-Farnhamton complex, protected,drained, 0 to 5 percent slopes

153—Ritz-Farnhamton complex, unprotected,drained, 0 to 5 percent slopes

157—Ritz-Schnoorson complex, protected,drained, 0 to 2 percent slopes

148—Riverwash159—Rock outcrop144—Rock outcrop-Jaypeak, very stony complex,

65 to 100 percent slopes149—Rock outcrop-McArthur, very stony complex,

65 to 100 percent slopes162—Rock outcrop-Treble, very stony complex,

5 to 35 percent slopes163—Rock outcrop-Treble, very stony complex,

35 to 65 percent slopes158—Roman, extremely bouldery-Rock outcrop

complex, 35 to 65 percent slopes165—Rubson ashy silt loam, 0 to 2 percent slopes166—Rubson ashy silt loam, 2 to 8 percent slopes167—Rubson ashy silt loam, 8 to 15 percent

slopes168—Rubycreek medial silt loam, 15 to 35 percent

slopes, very bouldery169—Rubycreek medial silt loam, 35 to 65 percent

slopes, very bouldery164—Rubycreek medial silt loam, moist, 30 to 55

percent slopes, very bouldery

170—Schnoorson silt loam, protected, drained,0 to 2 percent slopes

173—Schnoorson silty clay loam, protected,drained, 0 to 2 percent slopes

187—Schnoorson-DeVoignes complex, protected,drained, 0 to 2 percent slopes

171—Seelovers silt loam, 0 to 2 percent slopes172—Seelovers silt loam, drained, 0 to 2 percent

slopes199—Seelovers-Typic Fluvaquents-Aquic

Udifluvents complex, 0 to 4 percent slopes174—Selle ashy fine sandy loam, 0 to 7 percent

slopes175—Selle-Elmira complex, 0 to 20 percent slopes176—Snowlake ashy sandy loam, 12 to 35 percent

slopes177—Snowlake ashy sandy loam, 35 to 65 percent

slopes188—Stien ashy silt loam, 2 to 8 percent slopes182—Stien cobbly ashy silt loam, 2 to 8 percent

slopes179—Stien gravelly ashy silt loam, 2 to 8 percent

slopes198—Stien gravelly ashy silt loam, moist, 2 to 8

percent slopes186—Treble gravelly ashy sandy loam, 15 to 35

percent slopes185—Treble gravelly ashy sandy loam, 35 to 65

percent slopes184—Treble, very bouldery-Rock outcrop complex,

35 to 65 percent slopes202—Water190—Wishbone-Caboose complex, 35 to 75

percent slopes193—Zee ashy silt loam, 2 to 15 percent slopes194—Zee ashy silt loam, 15 to 35 percent slopes192—Zioncreek-Porthill complex, 2 to 8 percent

slopes195—Zioncreek-Porthill complex, 8 to 15 percent

slopes

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Summary of Tables

Temperature and Precipitation ................................................................................................ 6

Freeze Dates in Spring and Fall ............................................................................................. 7

Growing Season ..................................................................................................................... 8

For tables with the most current data, please visit theSoil Data Mart at http://soildatamart.nrcs.usda.gov/.

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Soil Survey ofBoundary County Area, Idaho

Use and Management of the Soils

This soil survey is an inventory and evaluation ofthe soils in the survey area. It can be used to adjustland uses to the limitations and potentials of naturalresources and the environment. Also, it can help toprevent soil-related failures in land uses.

In preparing a soil survey, soil scientists,conservationists, engineers, and others collectextensive field data about the nature and behavioralcharacteristics of the soils. They collect data onerosion, droughtiness, flooding, and other factors thataffect various soil uses and management. Fieldexperience and collected data on soil properties andperformance are used as a basis in predicting soilbehavior.

Information in this section can be used to plan theuse and management of soils for crops and pasture;as forestland; as sites for buildings, sanitary facilities,highways and other transportation systems, andparks and other recreational facilities; for agriculturalwaste management; and as wildlife habitat. It can beused to identify the potentials and limitations of eachsoil for specific land uses and to help preventconstruction failures caused by unfavorable soilproperties.

Planners and others using soil survey informationcan evaluate the effect of specific land uses onproductivity and on the environment in all or part ofthe survey area. The survey can help planners tomaintain or create a land use pattern in harmony withthe natural soil.

Contractors can use this survey to locate sourcesof sand and gravel, roadfill, and topsoil. They can useit to identify areas where bedrock, wetness, or veryfirm soil layers can cause difficulty in excavation.

Health officials, highway officials, engineers, andothers may also find this survey useful. The survey

can help them plan the safe disposal of wastes andlocate sites for pavements, sidewalks, campgrounds,playgrounds, lawns, and trees and shrubs.

Interpretive Ratings

The interpretive tables in this survey rate the soilsin the survey area for various uses. Many of thetables identify the limitations that affect specifieduses and indicate the severity of those limitations.The ratings in these tables are both verbal andnumerical.

Rating Class Terms

Rating classes are expressed in the tables interms that indicate the extent to which the soils arelimited by all of the soil features that affect a specifieduse or in terms that indicate the suitability of the soilsfor the use. Thus, the tables may show limitationclasses or suitability classes. Terms for the limitationclasses are not limited, somewhat limited, and verylimited. The suitability ratings are expressed as wellsuited, moderately suited, poorly suited, and unsuitedor as good, fair, and poor.

Numerical Ratings

Numerical ratings in the tables indicate the relativeseverity of individual limitations. The ratings areshown as decimal fractions ranging from 0.00 to 1.00.They indicate gradations between the point at whicha soil feature has the greatest negative impact on theuse and the point at which the soil feature is not alimitation. The limitations appear in order from themost limiting to the least limiting. Thus, if more thanone limitation is identified, the most severe limitationis listed first and the least severe one is listed last.

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Agronomy

General management needed for crops andpasture is suggested in this section. The estimatedyields of the main crops and pasture plants are listed,the system of land capability classification used bythe Natural Resources Conservation Service isexplained, and prime farmland is described.

Planners of management systems for individualfields or farms should consider the detailedinformation given in the description of each soil underthe heading “Detailed Soil Map Units.” Specificinformation can be obtained from the local office ofthe Natural Resources Conservation Service or theCooperative Extension Service.

Crops and PastureMichael Gondek, District Conservationist, NRCS, prepared this

section.

The Boundary County Area containsapproximately 60,000 acres of nonirrigated cropland,pasture, and hayland (figs. 9 and 10). The majority ofland used for crops, pasture, and hay is locatedadjacent to the Kootenai River.

The main crops grown in the survey area arespring wheat, winter wheat, oats, barley, alfalfa hay,clover seed, timothy seed, canola, and hops. A small,but significant acreage is used for ornamentalnursery production of both deciduous and coniferousplants. Most of the soils in the bottomland along theKootenai River are drained by a system of openditches and pumps and protected from flooding by asystem of levees. Maintaining these systems isessential for crop production.

The soils on the high benches and terraces aresubject to erosion where they are sloping. When grainis grown, crop residue should be left on the surface tomaintain the organic matter content and tilth of thesoil and to control erosion. Conservation tillagesystems are essential in the management of thesesoils. Crop residue on the soil surface is mostimportant during the fall and winter months to protectthe soil from erosion. Use of minimum tillage, no-tillpractices, cross-slope farming, or conservation-cropping systems is advisable.

Grain generally responds to nitrogen and sulfurfertilizer, and legumes respond to phosphorus. Agood fertilization program, including soil testing, isessential for the highest grain production.

Hay crops consist of alfalfa and alfalfa-grassmixed. With correct harvest management, twocuttings can be obtained in most years. During wetteryears, a third cutting can also be made. A significantacreage of timothy hay is grown in the area. Oats andbarley are also grown as a hay crop when they areused in rotation to renew alfalfa stands. Haylandmanagement can be improved by using properfertilizers as needed, cutting hay when it is at theproper growth stage, and leaving an adequateamount of fall stubble to protect the plants during thewinter.

Pastures in the survey area are relatively small.A combination of adapted grasses and legumesare generally used. Because of the small acreage,pasture can be susceptible to overgrazing. Whenfields are continually overgrazed throughout theyear, the production of good forage is reduced; thefields are invaded by less palatable or weedy plants;and soil erosion occurs on sloping areas.Overgrazing fields adjacent to creeks and streamscan cause streambank degradation, damageriparian vegetation, and reduce water qualitydownstream.

Improved management practices are needed toobtain high level yields of pasture. Suggestedpractices are controlled grazing systems, cross-fencing, water developments, and allowing adequateperiods for regrowth. The use of high-producingadapted plants and a fertilizer program are essentialto achieve high yields. A fertilizer program shouldinclude the application of nitrogen, phosphorus, andsulfur according to soil test results.

Livestock grazing should be carefully controlled.Animals should not be allowed to graze too early inthe spring before plants have reached adequategrowth and the soils are firm enough to withstandtrampling. Grasses should not be grazed so closethat they start regrowth from root-stored foodreserves. For most grasses, leaving a stubble heightof 4 inches at the end of the grazing period will allow

6 Soil Survey

for rapid recovery. These practices will help limit soilcompaction and protect the soil from erosion.

Yields per Acre

The average yields per acre that can be expectedof the principal crops under a high level ofmanagement are shown in the “Land Capability andYields per Acre of Crops and Pasture” tables. In anygiven year, yields may be higher or lower than thoseindicated in the tables because of variations in rainfalland other climatic factors. The land capabilityclassification of each map unit in the survey area isshown in the tables.

Yields are estimates based mainly on theexperience and records of farmers, conservationists,and extension agents. Available yield data fromnearby counties and results of field trials anddemonstrations are also considered.

The management needed to obtain the indicatedyields of the various crops depends on the kind of

soil and the crop. Management practices can includeimproving drainage, controlling erosion, andprotecting areas from flooding; selecting properplanting and seeding rates; choosing suitable high-yielding crop varieties; appropriately and timely tilling;controlling weeds, plant diseases, and harmfulinsects; ensuring favorable soil reaction and optimumlevels of nitrogen, phosphorus, potassium, andtrace elements for each crop; effectively using cropresidue, barnyard manure, and green-manure crops;and harvesting to ensure the smallest possible loss.

The estimated yields reflect the productivecapacity of each soil for each of the principal crops.Yields are likely to increase as new productiontechnology is developed. The productivity of a givensoil compared with that of other soils, however, is notlikely to change.

Crops other than those shown in the tables aregrown in the survey area, but estimated yields are notlisted because the acreage of such crops is small.

Figure 9.—In the Kootenai Valley, in the foreground, is an area of Rubson ashy silt loam, 2 to 8 percent slopes, that is used for hay,pasture, and timber production. Along the Kootenai River flood plain, in the middle ground, is an area of Schnoorson silt loam,protected, drained, 0 to 2 percent slopes, that is used for wheat, barley, and canola production.

Boundary County Area, Idaho—Part II 7

Local offices of the Natural ResourcesConservation Service or the Cooperative ExtensionService can provide information about themanagement and productivity of the soils for thosecrops.

Land Capability ClassificationLand capability classification shows, in a general

way, the suitability of soils for most kinds of fieldcrops (USDA, 1961). Crops that require specialmanagement are excluded. The soils are groupedaccording to their limitations for field crops, the riskof damage if they are used for crops, and the waythey respond to management. The criteria used ingrouping the soils do not include major and generallyexpensive landforming that would change slope,depth, or other characteristics of the soils, nor dothey include possible but unlikely major reclamationprojects. Capability classification is not a substitute

for interpretations designed to show suitability andlimitations of groups of soils for grazingland, forforestland, or for engineering purposes.

In the capability system, soils are generallygrouped at three levels—capability class, subclass,and unit.

Capability classes, the broadest groups, aredesignated by the numbers 1 through 8. Thenumbers indicate progressively greater limitationsand narrower choices for practical use. The classesare defined as follows:

Class 1 soils have slight limitations that restricttheir use.

Class 2 soils have moderate limitations thatrestrict the choice of plants or that require moderateconservation practices.

Class 3 soils have severe limitations thatrestrict the choice of plants or that require specialconservation practices, or both.

Figure 10.—In the foreground is an area of Ritz-Schnoorson complex, protected, drained, 0 to 2 percent slopes, that is used forwheat production. In the middle ground is an area of Caboose-Wishbone complex, 15 to 35 percent slopes, that is used fortimber production and pasture. In the background is an area of Dufort ashy silt loam, 35 to 65 percent slopes, that is used fortimber production and wildlife habitat.

8 Soil Survey

Class 4 soils have very severe limitations thatrestrict the choice of plants or that require verycareful management, or both.

Class 5 soils are subject to little or no erosion buthave other limitations, impractical to remove, thatrestrict their use mainly to pasture, grazingland,forestland, or wildlife habitat.

Class 6 soils have severe limitations that makethem generally unsuitable for cultivation and thatrestrict their use mainly to pasture, grazingland,forestland, or wildlife habitat.

Class 7 soils have very severe limitations thatmake them unsuitable for cultivation and that restricttheir use mainly to grazingland, forestland, or wildlifehabitat.

Class 8 soils and miscellaneous areas havelimitations that preclude commercial plantproduction and that restrict their use to recreationalpurposes, wildlife habitat, watershed, or estheticpurposes.

Capability subclasses are soil groups within oneclass. They are designated by adding a small letter,e, w, s, or c, to the class numeral, for example, 2e.The letter e shows that the main hazard is the riskof erosion unless close-growing plant cover ismaintained; w shows that water in or on the soilinterferes with plant growth or cultivation (in somesoils the wetness can be partly corrected by artificialdrainage); s shows that the soil is limited mainlybecause it is shallow, droughty, or stony; and c, usedin only some parts of the United States, shows thatthe chief limitation is climate that is very cold or verydry.

In class 1 there are no subclasses because thesoils of this class have few limitations. Class 5contains only the subclasses indicated by w, s, or cbecause the soils in class 5 are subject to little or noerosion. They have other limitations that restrict theiruse to pasture, grazingland, forestland, wildlifehabitat, or recreation.

Capability units are soil groups within a subclass.The soils in a capability unit are enough alike to besuited to the same crops and pasture plants, torequire similar management, and to have similarproductivity. Capability units are generally designatedby adding an Arabic numeral to the subclass symbol,for example, 2e-4 and 3e-6. These units are not givenin all soil surveys.

The capability classification of map units in thissurvey area is given in the “Land Capability andYields per Acre of Crops and Pasture” tables.

Prime FarmlandPrime farmland is one of several kinds of important

farmland defined by the U.S. Department ofAgriculture. It is of major importance in meeting theNation’s short- and long-range needs for food andfiber. Because the supply of high-quality farmland islimited, the U.S. Department of Agriculture recognizesthat responsible levels of government, as well asindividuals, should encourage and facilitate the wiseuse of our Nation’s prime farmland.

Prime farmland, as defined by the U.S. Departmentof Agriculture, is land that has the best combinationof physical and chemical characteristics for producingfood, feed, forage, fiber, and oilseed crops and isavailable for these uses. It could be cultivated land,pasture, forestland, or other land, but it is not urbanor built-up land or water areas. The soil qualities,growing season, and moisture supply are thoseneeded for the soil to economically producesustained high yields of crops when propermanagement, including water management, andacceptable farming methods are applied. In general,prime farmland has an adequate and dependablesupply of moisture from precipitation or irrigation, afavorable temperature and growing season,acceptable acidity or alkalinity, an acceptable salt andsodium content, and few or no rocks. It is permeableto water and air. It is not excessively erodible orsaturated with water for long periods, and it either isnot frequently flooded during the growing season oris protected from flooding. Slope ranges mainly from0 to 6 percent. More detailed information about thecriteria for prime farmland is available at the localoffice of the Natural Resources ConservationService.

The map units in the survey area that areconsidered prime farmland are listed in the “PrimeFarmland” table. This list does not constitute arecommendation for a particular land use. On somesoils included in the list, measures that overcome ahazard or limitation, such as flooding, wetness, anddroughtiness, are needed. Onsite evaluation isneeded to determine whether or not the hazard orlimitation has been overcome by correctivemeasures. The extent of each listed map unit isshown in the “Acreage and Proportionate Extent ofthe Soils” table. The location is shown on the detailedsoil maps. The soil qualities that affect use andmanagement are described in the section “DetailedSoil Map Units.”

23

Grazingland

In areas that have similar climate and topography,differences in the kind and amount of grazeablevegetation are closely related to the kind of soil.Effective management is based on the relationshipbetween the soils and vegetation and water.

The “Grazingland and Grazeable Understory-Productivity and Characteristic Plant Communities”table shows, for each soil that supports understoryvegetation and for each soil that supports vegetationsuitable for grazing, the ecological site; the totalannual production of vegetation in favorable, normal,and unfavorable years; the characteristic nativevegetation; and the composition, by percentage ofair-dry weight, of each species.

An ecological site is the product of all theenvironmental factors responsible for itsdevelopment. It has characteristic soils that havedeveloped over time throughout the soil developmentprocess; a characteristic hydrology, particularlyinfiltration and runoff, that has developed over time;and a characteristic plant community (kind andamount of vegetation). The hydrology of the site isinfluenced by development of the soil and plantcommunity. The vegetation, soils, and hydrology areall interrelated. Each is influenced by the others andinfluences the development of the others. The plantcommunity on an ecological site is typified by anassociation of species that differs from that of otherecological sites in the kind and/or proportion ofspecies or in total production (Cooper and others,1991). Descriptions of ecological sites are provided inthe Field Office Technical Guide, which is available inlocal offices of the Natural Resources ConservationService.

Woodland Understory VegetationThe table shows, for each soil suitable for

woodland, the potential for producing understoryvegetation. The total dry-weight production forunderstory vegetation includes the herbaceous plantsand the leaves, twigs, and fruit of woody plants up toa height of 4.5 feet. It is expressed in pounds per acreof air-dry vegetation in favorable, normal, and

unfavorable years. In a favorable year, soil moisture isabove average during the optimum part of thegrowing season; in a normal year, soil moisture isaverage; and in an unfavorable year, it is belowaverage. Yields are adjusted to a common percent ofair-dry moisture content.

Characteristic native vegetation—the grasses,forbs, shrubs, and other plants that make up theunderstory natural plant community on each soil—islisted by common name. Forestland compositionshows the expected percentage of the total annualproduction for each understory plant species under acanopy density that is most nearly typical ofwoodland in which the production of wood crops ishighest.

The amount of characteristic native vegetationthat can be used as forage depends on the kinds ofgrazing animals and on the grazing season. If wellmanaged, some woodland can produce enoughunderstory vegetation to support grazing of livestockor wildlife, or both, without damage to the trees.

The quantity and quality of understory vegetationvary with the kind of soil, the age and kind of trees inthe canopy, the density of the canopy, and the depthand condition of the litter. The density of the canopydetermines the amount of light that understory plantsreceive.

Grazingland VegetationTotal dry-weight production is the amount of

vegetation that can be expected to grow annually in awell-managed opened area that is supporting theopen natural plant community. It includes allvegetation, whether or not it is palatable to grazinganimals. It includes the current year’s growth ofleaves, twigs, and fruits of woody plants. It does notinclude the increase in stem diameter of trees andshrubs. It is expressed in pounds per acre of air-dryvegetation for favorable, normal, and unfavorableyears. In a favorable year, the amount and distributionof precipitation and the temperatures make growingconditions substantially better than average. In anormal year, growing conditions are about average. In

24 Soil Survey

an unfavorable year, growing conditions are wellbelow average, generally because of low availablesoil moisture. Yields are adjusted to a commonpercent of air-dry moisture content.

Characteristic native vegetation—the grasses,forbs, and shrubs that make up most of the opennatural plant community on each soil—is listed bycommon name. Grazingland composition shows theexpected percentage of the total annual productionfor each grazeable plant species making up thecharacteristic native vegetation. The amount that canbe used as forage depends on the kinds of grazinganimals and on the grazing season.

Woodland GrazingFrank Gariglio, Forester, NRCS, and Michael Gondek, District

Conservationist, NRCS, prepared this section.

Many of the native plants that occur in the forestunderstory can provide grazing opportunities for

livestock and big game animals (fig. 11). Introducedplants, generally grasses and legumes, that havebeen seeded on road cuts and fill slopes and onharvested or disturbed areas within the forest areadditional forage sources for livestock. Livestockgrazing is usually a lower priority for privatelandowners when compared to timber production onforestlands. Yet, managed understory and forestgrazing can provide significant annual economicbenefits for the private forestland user andlandowner.

Forested soils found at lower elevations in thesurvey area are usually warmer and drier but offer alonger grazing season for livestock when comparedto those soils found in higher elevations. Additionally,soils identified at the higher elevations of the surveyarea often have less livestock grazing use because ofthe very steep terrain and the higher percentage oftall brush species in the understory.

The amount and quality of light that reaches theground affects plants growing beneath the tree

Figure 11.—In the foreground is an area of Stien gravelly ashy silt loam, 2 to 8 percent slopes, that is used for timber productionand pasture. In the middle ground is an area of Pend Oreille ashy silt loam, 35 to 65 percent slopes, that is used for timberproduction. In the background is an area of Jaypeak gravelly ashy silt loam, 35 to 75 percent slopes, that is used for timberproduction and wildlife habitat.

Boundary County Area, Idaho—Part II 25

canopy. In general, under the dense canopy of a fullystocked, mature forest, usable livestock forage is atthe lowest level for the rotation of the stand. Incontrast, where logging, fire, or other similardisturbance reduces the density of the forest canopy,the amount and kind of usable livestock forageincrease because of the increase in sunlight andmoisture that reaches the forest floor. The length oftime required to complete the rotation from openseedling/sapling stage to older, mature, densecanopy stands and the corresponding variability inavailable forage depends on the specific plantcommunity (Cooper and others, 1991), soil, climate,and other factors, such as management actions thatare taken on the site. The potential for forageproduction for opened canopy forests in a well-managed condition is shown in the “Grazingland andGrazeable Understory-Productivity and CharacteristicPlant Communities” table.

Cattle tend to concentrate in those areas within theforest that are the easiest to access and travelthrough, or that provide for all of their daily needs for

feed, water, and shelter within a short distance. Forthese reasons, riparian zones, meadows, and forestroads are all common areas for heavy cattle usage.Any concentration of livestock can result inovergrazing and other damage to the more palatableor sensitive plants. This in turn can lead to acorresponding increase in potential damage toriparian areas, road banks, or other soil resources.Using salt to encourage cattle to use areas furtheraway from concentration zones, livestock herding,strategic water placement, establishing trails, andfence usage are all common livestock managementpractices utilized in woodland grazing systems.Seeding mixtures used in stabilizing road cut and fillslopes should be selected to minimize overuse bylivestock.

Livestock grazing management should bebalanced with other resource concerns within theforest. Some of the other resource concerns toaddress include water quality, wildlife habitat,aesthetic values, and the silvicultural goals of thelandowner.

51

Forestland

Forestland Management andProductivity

The tables in this section can help forest owners ormanagers plan the use of soils for wood crops. Theyshow the potential productivity of the soils for woodcrops and rate the soils according to the limitationsthat affect various aspects of forest management.

Forestland Management

In the “Forestland Management” tables,interpretive ratings are given for various aspects offorestland management. The ratings are both verbaland numerical.

Some rating class terms indicate the degree towhich the soils are suited to a specified forestmanagement practice. Well suited indicates that thesoil has features that are favorable for the specifiedpractice and has no limitations. Good performancecan be expected, and little or no maintenance isneeded. Moderately suited indicates that the soil hasfeatures that are moderately favorable for thespecified practice. One or more soil properties areless than desirable, and fair performance can beexpected. Some maintenance is needed. Poorlysuited indicates that the soil has one or moreproperties that are unfavorable for the specifiedpractice. Overcoming the unfavorable propertiesrequires special design, extra maintenance, andcostly alteration. Unsuited indicates that theexpected performance of the soil is unacceptablefor the specified practice or that extreme measuresare needed to overcome the undesirable soilproperties.

Numerical ratings in the tables indicate the severityof individual limitations. The ratings are shown asdecimal fractions ranging from 0.00 to 1.00. Theyindicate gradations between the point at which a soilfeature has the greatest negative impact on thespecified forest management practice (1.00) and thepoint at which the soil feature is not a limitation(0.00).

Rating class terms for fire damage and seedlingmortality are expressed as low, moderate, and high.Where these terms are used, the numerical ratingsindicate gradations between the point at which thepotential for fire damage or seedling mortality ishighest (1.00) and the point at which the potential islowest (0.00).

The paragraphs that follow indicate the soilproperties considered in rating the soils for forestmanagement practices. More detailed informationabout the criteria used in the ratings is available inthe “National Forestry Handbook.”

For limitations affecting construction of haul roadsand log landings, the ratings are based on slope,flooding, permafrost, plasticity index, the hazard ofsoil slippage, content of sand, the Unifiedclassification, rock fragments on or below the surface,depth to a restrictive layer that is indurated, depth toa water table, and ponding. The limitations aredescribed as slight, moderate, or severe. A rating ofslight indicates that no significant limitations affectconstruction activities, moderate indicates that one ormore limitations can cause some difficulty inconstruction, and severe indicates that one or morelimitations can make construction very difficult or verycostly.

The ratings of suitability for log landings are basedon slope, rock fragments on the surface, plasticityindex, content of sand, the Unified classification,depth to a water table, ponding, flooding, and thehazard of soil slippage. The soils are described aswell suited, moderately suited, or poorly suited to useas log landings.

Ratings in the column soil rutting hazard are basedon depth to a water table, rock fragments on or belowthe surface, the Unified classification, depth to arestrictive layer, and slope. Ruts form as a result ofthe operation of forest equipment. The hazard isdescribed as slight, moderate, or severe. A rating ofslight indicates that the soil is subject to little or norutting; moderate indicates that rutting is likely; andsevere indicates that ruts form readily.

Ratings in the column hazard of off-road or off-trailerosion are based on slope and on soil erodibility

52 Soil Survey

factor K. The soil loss is caused by sheet or rillerosion in off-road or off-trail areas where 50 to75 percent of the surface has been exposed bylogging, grazing, mining, or other kinds ofdisturbance. The hazard is described as slight,moderate, severe, or very severe. A rating of slightindicates that erosion is unlikely under ordinaryclimatic conditions; moderate indicates that someerosion is likely and that erosion-control measuresmay be needed; severe indicates that erosion is verylikely and that erosion-control measures, includingrevegetation of bare areas, are advised; and verysevere indicates that significant erosion is expected,loss of soil productivity and off-site damage are likely,and erosion-control measures are costly andgenerally impractical.

Ratings in the column hazard of erosion on roadsand trails are based on the soil erodibility factor K,slope, and content of rock fragments. The ratingsapply to unsurfaced roads and trails. The hazard isdescribed as slight, moderate, or severe. A rating ofslight indicates that little or no erosion is likely;moderate indicates that some erosion is likely, thatthe roads or trails may require occasionalmaintenance, and that simple erosion-controlmeasures are needed; and severe indicates thatsignificant erosion is expected, that the roads or trailsrequire frequent maintenance, and that costlyerosion-control measures are needed.

Ratings in the column suitability for roads (naturalsurface) are based on slope, rock fragments on thesurface, plasticity index, content of sand, the Unifiedclassification, depth to a water table, ponding,flooding, and the hazard of soil slippage. The ratingsindicate the suitability for using the natural surface ofthe soil for roads. The soils are described as wellsuited, moderately suited, or poorly suited to this use.

Ratings in the columns suitability for hand plantingand suitability for mechanical planting are based onslope, depth to a restrictive layer, content of sand,plasticity index, rock fragments on or below thesurface, depth to a water table, and ponding. Thesoils are described as well suited, moderately suited,poorly suited, or unsuited to these methods ofplanting. It is assumed that necessary sitepreparation is completed before seedlings areplanted.

Ratings in the column suitability for use ofharvesting equipment are based on slope, rockfragments on the surface, plasticity index, content ofsand, the Unified classification, depth to a watertable, and ponding. The soils are described as wellsuited, moderately suited, or poorly suited to this use.

Ratings in the column suitability for mechanicalsite preparation (surface) are based on slope, depthto a restrictive layer, plasticity index, rock fragmentson or below the surface, depth to a water table, andponding. The soils are described as well suited,poorly suited, or unsuited to this management activity.The part of the soil from the surface to a depth ofabout 1 foot is considered in the ratings.

Ratings in the column suitability for mechanicalsite preparation (deep) are based on slope, depth toa restrictive layer, rock fragments on or below thesurface, depth to a water table, and ponding. Thesoils are described as well suited, poorly suited, orunsuited to this management activity. The part of thesoil from the surface to a depth of about 3 feet isconsidered in the ratings.

Ratings in the column potential for damage to soilby fire are based on texture of the surface layer,content of rock fragments and organic matter in thesurface layer, thickness of the surface layer, andslope. The soils are described as having a low,moderate, or high potential for this kind of damage.The ratings indicate an evaluation of the potentialimpact of prescribed fires or wildfires that are intenseenough to remove the duff layer and consumeorganic matter in the surface layer.

Ratings in the column potential for seedlingmortality are based on flooding, ponding, depth to awater table, content of lime, reaction, salinity,available water capacity, soil moisture regime, soiltemperature regime, aspect, and slope. The soils aredescribed as having a low, moderate, or highpotential for seedling mortality.

Forestland Productivity

In the “Forestland Productivity” table, the potentialproductivity of merchantable or common trees on asoil is expressed as a site index and as a volumenumber. The site index is the average height, in feet,that dominant and codominant trees of a givenspecies attain in a specified number of years(Alexander, 1967; Cochran, 1979a; Cochran, 1979b;Cochran, 1979c; Haig, 1932; Meyer, 1961; Schmidtand others, 1976). The site index applies to fullystocked, even-aged, unmanaged stands. Commonlygrown trees are those that forest managersgenerally favor in intermediate or improvementcuttings. They are selected on the basis of growthrate, quality, value, and marketability. More detailedinformation regarding site index is available inthe “National Forestry Handbook” (USDA, 1998),which is available in local offices of the Natural

Boundary County Area, Idaho—Part II 53

Resources Conservation Service or on the Internet(http://soils.usda.gov/technical/).

The volume of wood fiber, a number, is the yieldlikely to be produced by the most important treespecies. This number, expressed as cubic feet peracre per year and calculated at the age ofculmination of the mean annual increment (CMAI),indicates the amount of fiber produced in a fullystocked, even-aged, unmanaged stand.

Trees to manage are those that are preferred forplanting, seeding, or natural regeneration and thosethat remain in the stand after thinning or partialharvest.

Forestland in the Boundary CountyArea

Frank Gariglio, Forester, NRCS, and Michael Gondek, DistrictConservationist, NRCS, prepared this section.

The forest product industry began in BoundaryCounty around 1890 with limited logging of the localforests and the corresponding establishment of smallsawmill operations. Within a few years, more millswere established throughout the area and a variety offorest products were being manufactured. Despitemany up- and downturns in the demand for woodproducts during the past century, the forest productsindustry continues to be a dominant economic forcein the soil survey area (fig. 12).

The most extensive conifer species in the soilsurvey area are ponderosa pine, Douglas-fir, grandfir, western white pine, lodgepole pine, westernhemlock, western red cedar, western larch, subalpinefir, and Engelmann spruce. Other species of lesserextent include subalpine larch and mountain hemlock.Cottonwood, quaking aspen, and birch occur on thewetter soils and along riparian zones.

Tree growth rates and the species of trees thatgrow on a particular site vary according to soil types.Soil depth, chemistry, texture, and available water-holding capacity in combination with aspect,elevation, and precipitation are some of the majorenvironmental factors that influence tree speciesoccurrences and growth rates.

This soil survey provides more detailedinterpretations of the forested soils identified in thesoil survey area. However, the following table isuseful in identifying general soil and climaticinfluences on the common trees in the area.

Relative Silvical Characteristics of the Common Forest Treesin the Boundary County Soil Survey Area1

______________________________________________________

Tolerance Low Moderate Highto:

Shade WL LP PP WP DF ES GF AF WCWHFrost WH WC GF PP WL DF WP AF ES LPDrought WH WC AF ES WP GF WL LP DF PPFire resistance WH WC AF ES WP GF WL LP DF PPExcess water PP DF WL GF WP AF WH ES WC LP

AF Subalpine fir PP Ponderosa pineDF Douglas-fir WC Western red cedarES Engelmann spruce WH Western hemlockGF Grand fir WL Western larchLP Lodgepole pine WP Western white pine

______________________________________________________

1Adapted from Fiedler, Carl E., and Lloyd, Dennis A. 1995. Autecology andsynecology of western larch. In ecology and management of larix forests: alook ahead.” Proceedings of an international symposium, Whitefish,Montana, U.S.A. October 5-9, 1992. U.S. Department of Agriculture, ForestService, Intermountain Research Station GTR-INT-319.

The historic occurrence of wildfires in the soilsurvey area heavily influenced the composition of theforests prior to the turn of the last century. Since thattime, the makeup of the trees found on most of theforest stands has been altered by fire suppression, aswell as by preferential harvest of the higher valuetrees during logging. In addition, western white pineis further compromised as a viable stand componentover its historic range because of the devastationcaused by white pine blister rust.

The topography of much of the forestlands in thesoil survey area consists of steep and very steepmountain slopes. The remainder of the area consistsof nearly level bottomlands on the Kootenai Riverflood plain and adjacent gently sloping benches inthe valley. Forest soils are also very steep on thedissected landforms and escarpments in theKootenai Valley. Forest harvesting methods areinfluenced by the steepness of the terrain. Slopes thatexceed 35 percent are generally not suitable forground machine skidding. On any ground-basedsystem, erosion, compaction, and displacement ofthe soil must be carefully managed. On slopessteeper than 35 percent, highlead or skyline systemsare utilized for harvesting timber.

Aspect, elevation, silvicultural history, seedbedcondition, and soil characteristics influence thesuccess of natural seedling germination, survival,and eventual establishment of mature trees within a

54 Soil Survey

Figure 12.—An area of Redraven medial silt loam, 35 to 65 percent slopes, bouldery, that is used for timber production and wildlifehabitat.

forest stand. Most of the soils in the soil survey areahave a surface layer of varying thicknesses that has ahigh content of volcanic ash. The content of volcanicash adds to the moisture and nutrient-holdingcapacity of the soils, which influences tree growthrates. Brackenfern and alder brush competition ispresent on many of the higher elevation forest soils.In many instances, the removal of the tree canopyhas resulted in long-term suppression of the potentialtree regeneration on these sites because of thesevere brush competition.

Careful placement and construction of loggingroads and skidtrails, with erosion stabilizationpractices installed prior to use, are necessary toprevent erosion and sedimentation on many of theforest soils in the soil survey area, especially for soils

on steeper landforms. This soil survey identifiesseveral soils with subsoil material that can eroderapidly when exposed during road building. Soilslippage and landslides can also be a problem onsome of the steep soils, especially those identified onthe terrace escarpments found in the Kootenai Rivervalley. Other forested soils in the valleys have a highwater table that makes the soil wetter for longerperiods throughout the year, leading to a highercompaction and displacement hazard.

The “Forestland Management” and “ForestlandProductivity” tables and the map unit descriptions inthe section, “Detailed Soil Map Units,” provide moreinformation on soil-related managementinterpretations and limitations.

119

Recreation

The soils of the survey area are rated in the“Recreation” tables according to limitations that affecttheir suitability for recreation. The ratings are bothverbal and numerical. Rating class terms indicate theextent to which the soils are limited by all of the soilfeatures that affect the recreational uses. Not limitedindicates that the soil has features that are veryfavorable for the specified use. Good performanceand very low maintenance can be expected.Somewhat limited indicates that the soil has featuresthat are moderately favorable for the specified use.The limitations can be overcome or minimized byspecial planning, design, or installation. Fairperformance and moderate maintenance can beexpected. Very limited indicates that the soil has oneor more features that are unfavorable for the specifieduse. The limitations generally cannot be overcomewithout major soil reclamation, special design, orexpensive installation procedures. Poor performanceand high maintenance can be expected.

Numerical ratings in the tables indicate the severityof individual limitations. The ratings are shown asdecimal fractions ranging from 0.00 to 1.00. Theyindicate gradations between the point at which a soilfeature has the greatest negative impact on the use(1.00) and the point at which the soil feature is not alimitation (0.00).

The ratings in the tables are based on restrictivesoil features, such as wetness, slope, and texture ofthe surface layer. Susceptibility to flooding isconsidered. Not considered in the ratings, butimportant in evaluating a site, are the location andaccessibility of the area, the size and shape of thearea and its scenic quality, vegetation, access towater, potential water impoundment sites, and accessto public sewer lines. The capacity of the soil toabsorb septic tank effluent and the ability of the soilto support vegetation also are important. Soils thatare subject to flooding are limited for recreationaluses by the duration and intensity of flooding and theseason when flooding occurs. In planningrecreational facilities, onsite assessment of the

height, duration, intensity, and frequency of floodingis essential. The information in the “Recreation”tables can be supplemented by other information inthis survey, for example, interpretations for buildingsite development, construction materials, sanitaryfacilities, and water management.

Camp areas require site preparation, such asshaping and leveling the tent and parking areas,stabilizing roads and intensively used areas, andinstalling sanitary facilities and utility lines. Campareas are subject to heavy foot traffic and somevehicular traffic. The ratings are based on the soilproperties that affect the ease of developing campareas and the performance of the areas afterdevelopment. Slope, stoniness, and depth to bedrockor a cemented pan are the main concerns affectingthe development of camp areas. The soil propertiesthat affect the performance of the areas afterdevelopment are those that influence trafficability andpromote the growth of vegetation, especially inheavily used areas. For good trafficability, the surfaceof camp areas should absorb rainfall readily, remainfirm under heavy foot traffic, and not be dusty whendry. The soil properties that influence trafficability aretexture of the surface layer, depth to a water table,ponding, flooding, permeability, and large stones. Thesoil properties that affect the growth of plants aredepth to bedrock or a cemented pan, permeability,and toxic substances in the soil.

Picnic areas are subject to heavy foot traffic. Mostvehicular traffic is confined to access roads andparking areas. The ratings are based on the soilproperties that affect the ease of developing picnicareas and that influence trafficability and the growthof vegetation after development. Slope and stoninessare the main concerns affecting the development ofpicnic areas. For good trafficability, the surface ofpicnic areas should absorb rainfall readily, remainfirm under heavy foot traffic, and not be dusty whendry. The soil properties that influence trafficability aretexture of the surface layer, depth to a water table,ponding, flooding, permeability, and large stones. The

120 Soil Survey

soil properties that affect the growth of plants aredepth to bedrock or a cemented pan, permeability,and toxic substances in the soil.

Playgrounds require soils that are nearly level, arefree of stones, and can withstand intensive foot traffic.The ratings are based on the soil properties thataffect the ease of developing playgrounds and thatinfluence trafficability and the growth of vegetationafter development. Slope and stoniness are the mainconcerns affecting the development of playgrounds.For good trafficability, the surface of the playgroundsshould absorb rainfall readily, remain firm underheavy foot traffic, and not be dusty when dry. The soilproperties that influence trafficability are texture ofthe surface layer, depth to a water table, ponding,flooding, permeability, and large stones. The soilproperties that affect the growth of plants are depth tobedrock or a cemented pan, permeability, and toxicsubstances in the soil.

Paths and trails for hiking and horseback ridingshould require little or no slope modification throughcutting and filling. The ratings are based on the soilproperties that affect trafficability and erodibility.These properties are stoniness, depth to a watertable, ponding, flooding, slope, and texture of thesurface layer.

Off-road motorcycle trails require little or no sitepreparation. They are not covered with surfacingmaterial or vegetation. Considerable compaction ofthe soil material is likely. The ratings are based on thesoil properties that influence erodibility, trafficability,dustiness, and the ease of revegetation. Theseproperties are stoniness, slope, depth to a watertable, ponding, flooding, and texture of the surfacelayer.

Golf fairways are subject to heavy foot traffic andsome light vehicular traffic. Cutting or filling may berequired. Irrigation is not considered in the ratings.The ratings are based on the soil properties that

affect plant growth and trafficability after vegetation isestablished. The properties that affect plant growthare reaction; depth to a water table; ponding; depth tobedrock or a cemented pan; the available watercapacity in the upper 40 inches; the content of salts,sodium, or calcium carbonate; and sulfidic materials.The properties that affect trafficability are flooding,depth to a water table, ponding, slope, stoniness, andthe amount of sand, clay, or organic matter in thesurface layer. The suitability of the soil for traps, tees,roughs, and greens is not considered in the ratings.

Recreation in the BoundaryCounty Area

The soil survey area is located in an exceptionalscenic and recreational part of Idaho. It includesforested mountains; two major rivers, the Kootenaiand Moyie; McArthur Lake; and many smaller lakesand streams. Fishing is good for all types of trout andother sport fishes. Deer, elk, moose, bear, and cougarinhabit the area, and big-game hunting is excellent.Grouse are plentiful in the forested, upland areas.The Kootenai National Wildlife Refuge and theMcArthur Lake State Wildlife Management Areaprovide important waterfowl habitat. Other wetlandareas along the Kootenai River and the many otherponds and streams throughout the area supplyadditional waterfowl habitat.

Many public and private campgrounds, resorts,and recreation areas offer excellent facilities forboating, fishing, and other outdoor activities.Opportunities exist for hiking and mountain bikingduring the summer and cross-country skiing andsnowmobiling during the winter. The increaseddemand for land to provide recreational facilities isexpected to continue for many years.

141

Wildlife Habitat

Soils affect the kind and amount of vegetation thatis available to wildlife as food and cover. Soils alsoaffect the construction of water impoundments. Thekind and abundance of wildlife depend largely on theamount and distribution of food, cover, and water.Wildlife habitat can be created or improved byplanting appropriate vegetation, by maintaining theexisting plant cover, or by promoting the naturalestablishment of desirable plants.

In the “Wildlife Habitat” table, the soils in thesurvey area are rated according to their potential forproviding habitat for various kinds of wildlife. Thisinformation can be used in planning parks, wildliferefuges, nature study areas, and other developmentsfor wildlife; in selecting soils that are suitable forestablishing, improving, or maintaining specificelements of wildlife habitat; and in determining theintensity of management needed for each element ofthe habitat.

The potential of the soil is rated good, fair, poor, orvery poor. A rating of good indicates that the elementor kind of habitat is easily established, improved, ormaintained. Few or no limitations affect management,and satisfactory results can be expected. A rating offair indicates that the element or kind of habitat canbe established, improved, or maintained in mostplaces. Moderately intensive management is requiredfor satisfactory results. A rating of poor indicates thatlimitations are severe for the designated element orkind of habitat. Habitat can be created, improved, ormaintained in most places, but management isdifficult and must be intensive. A rating of very poorindicates that restrictions for the element or kind ofhabitat are very severe and that unsatisfactory resultscan be expected. Creating, improving, or maintaininghabitat is impractical or impossible.

The elements of wildlife habitat are described inthe following paragraphs.

Grain and seed crops are domestic grains andseed-producing herbaceous plants. Soil propertiesand features that affect the growth of grain and seedcrops are depth of the root zone, texture of the

surface layer, available water capacity, wetness,slope, surface stoniness, and flooding. Soiltemperature and soil moisture also areconsiderations. Examples of grain and seed cropsare barley, canola, hops, oats, and wheat.

Grasses and legumes are domestic perennialgrasses and herbaceous legumes. Soil propertiesand features that affect the growth of grasses andlegumes are depth of the root zone, texture of thesurface layer, available water capacity, wetness,surface stoniness, flooding, and slope. Soiltemperature and soil moisture also areconsiderations. Examples of grasses and legumesare alfalfa, brome, clover, and fescue.

Wild herbaceous plants are native or naturallyestablished grasses and forbs, including weeds. Soilproperties and features that affect the growth of theseplants are depth of the root zone, texture of thesurface layer, available water capacity, wetness,surface stoniness, and flooding. Soil temperature andsoil moisture also are considerations. Examples ofwild herbaceous plants are false Solomon’s seal,pinegrass, showy aster, and wheatgrass.

Deciduous trees and woody understory producenuts or other fruit, buds, catkins, twigs, bark, andfoliage. Soil properties and features that affect thegrowth of deciduous trees and shrubs are depth ofthe root zone, available water capacity, and wetness.Examples of these plants are aspen, chokecherry,huckleberry, and red osier dogwood. Examples offruit-producing shrubs that are suitable for planting onsoils rated good are Russian-olive and crabapple.

Coniferous plants furnish browse and seeds. Soilproperties and features that affect the growth ofconiferous trees, shrubs, and ground cover are depthof the root zone, available water capacity, andwetness. Examples of coniferous plants are commonjuniper, Engelmann spruce, lodgepole pine,subalpine fir, western red cedar, and western whitepine.

Shrubs are bushy woody plants that produce fruit,buds, twigs, bark, and foliage. Soil properties and

142 Soil Survey

features that affect the growth of shrubs are depth ofthe root zone, available water capacity, salinity, andsoil moisture. Examples of shrubs are mallowninebark, redstem ceanothus, and snowberry.

Wetland plants are annual and perennial wildherbaceous plants that grow on moist or wet sites.Submerged or floating aquatic plants are excluded.Soil properties and features affecting wetland plantsare texture of the surface layer, wetness, reaction,salinity, slope, and surface stoniness. Examples ofwetland plants are cattail, rush, and sedge.

Shallow water areas have an average depth ofless than 5 feet. Some are naturally wet areas. Othersare created by dams, levees, or other water-controlstructures. Soil properties and features affectingshallow water areas are depth to bedrock, wetness,surface stoniness, slope, and permeability. Examplesof shallow water areas are marshes, ponds, andwaterfowl feeding areas.

Habitat for openland wildlife consists of cropland,pasture, meadows, and areas that are overgrown withgrasses, herbs, shrubs, and vines. These areasproduce grain and seed crops, grasses and legumes,and wild herbaceous plants. Wildlife attracted tothese areas include cottontail, meadowlark,pheasant, red fox, and savannah sparrow.

Habitat for woodland wildlife consists of areas ofdeciduous and/or coniferous plants and associatedgrasses, legumes, and wild herbaceous plants.Wildlife attracted to these areas include bear, deer,elk, ruffed grouse, squirrel, thrush, wild turkey, andwoodpecker.

Habitat for wetland wildlife consists of open,marshy or swampy shallow water areas. Wildlifeattracted to these areas include beaver, duck, geese,heron, mink, muskrat, and shore birds.

Wildlife of the Boundary CountyArea

Michael Gondek, District Conservationist, NRCS, and Frank J.Fink, Biologist, NRCS, prepared this section.

This section relates to the various uses that wildlifemake of the soils in the survey area. Locations ofdifferent wildlife species and their activities arereferenced to soil map unit numbers. The BoundaryCounty soil survey area supports a variety of gameand nongame fish and wildlife populations. Thequality of wildlife habitat depends on the soil, kindand amount of vegetation, and past management.

Big game animals in the survey area consist of elk,white-tailed deer, mule deer, black bear, and moose.Elk are well suited to the habitat of the area. Most of

the soil map units below 4,800-feet elevation providesummer and winter range for elk. These soil mapunits include 116, 126, 136, and 185. Elk migrate towinter range on south- and west-facing slopes below4,000-feet elevation along the major river valleys.Creating new brush fields and rehabilitating existingbrush fields on these winter ranges is critical tomaintaining elk herds at current levels. Above 4,800-feet elevation, soil map units, including 104, 155, 164,and 168, are used strictly for summer range.

Deer in the survey area include both white-taileddeer and mule deer. White-tailed deer comprise morethan half of the total deer population. White-taileddeer occupy the lower elevations, including soil mapunits 126, 166, 175, 179, and 190, along the valleysand river systems. Mule deer are more widely spreadand occupy areas including soil map units 104, 108,123, 124, 155, 164, 176, and 184.

A variety of upland game bird species use all ofthe different habitat types in the survey area. Threespecies of forest grouse—ruffed, blue, and spruce—inhabit forestland areas. Grouse occupy areas in soilmap units such as 107, 116, 117, 126, 136, 155, 166,and 174. Ruffed grouse spend the summer in openclearings within wooded areas and then winter inconifer forests. Blue grouse move to higher elevationsfor wintering, but their nesting habitat is usually atlower elevations on more open, grassy, or brush-covered slopes and ridges.

Furbearers, such as beaver, mink, muskrat, andotter, live in and around creeks, wetlands, and lakesin the survey area. Soil map units 171, 142, and 199comprise the major riparian zones in the area, butsmall creeks extend up into the foothills andmountains and provide additional riparian areas forthese furbearers.

Where appropriate conditions permit, bobcat,coyote, fisher, lynx, marten, mountain lion, andwolverine inhabit in the survey area.

Open water areas and wetlands exist throughoutthe survey area, making it a major waterfowl area.Nesting occurs mainly along rivers, streams, andsmall lakes or ponds. Most waterfowl activity occursin soil map units 151, 201, 142, 199, and 171. Peakfall migration of waterfowl occurs from mid Octoberthrough November. These migrating waterfowl willhold over at the Kootenai National Wildlife Refuge,McArthur Lake Wildlife Management Area, theKootenai River, and the many sloughs and pondsalong the valley. The major migrating species arebufflehead, Canada geese, gadwall, goldeneye,mallard, pintail, swan, teal, wigeon, and wood duck.

Several raptors use the entire survey area foreither all or part of their range. Some of the more

Boundary County Area, Idaho—Part II 143

common and highly visible raptors are bald eagle,red-tailed hawk, goshawk osprey, and a variety ofowls. The bald eagle is listed as a threatened speciesin the survey area, where there are active nestingsites. The bald eagle is mostly a winter visitor andfeeds along the rivers and ponds associated with soilmap units 119, 151, 142, 201, 199, and 171.

The main sport fisheries in the major rivers andstreams of the survey area are rainbow trout,cutthroat trout, and mountain whitefish. Tributarystreams contain significant spawning and rearinghabitats for Kokanee salmon, rainbow trout, cutthroattrout, and brook trout. The Kootenai River has bulltrout, white sturgeon, and ling (burbot). Bull trout andwhite sturgeon are listed as threatened andendangered under the U.S. Endangered Species Act.There are numerous small lakes containinglargemouth bass, crappie, perch, bluegill, and varioustrout species.

The wildlife population in the survey area is largelydetermined by habitat suitability, including the foodsupply, amount of cover, and water availability.Habitats differ in their capacity to provide theseessential needs. Some of these deficiencies arebecause of the characteristics of the soils, and othersare the result of management.

Populations of game and nongame species can beenhanced by using conservation practices to improvetheir habitat. These practices include development ofodd or irregularly shaped areas in and adjacent tofarmland to provide food and cover, protection ofhabitat from fire or grazing, and establishment ofwoody vegetation to provide winter shelter. Wildlifehabitat may also be enhanced through application ofcommonly employed conservation practices includingminimum tillage, planned grazing systems, pondconstruction, shelterbelts and field windbreaks, andstripcropping.

153

Engineering

This section provides information for planning landuses related to urban development and to watermanagement. Soils are rated for various uses, andthe most limiting features are identified. Ratings aregiven for building site development, sanitary facilities,construction materials, and water management. Theratings are based on observed performance of thesoils and on the estimated data and test data in the“Soil Properties” section.

Information in this section is intended for land useplanning, for evaluating land use alternatives, and forplanning site investigations prior to design andconstruction. The information, however, haslimitations. For example, estimates and other datagenerally apply only to that part of the soil betweenthe surface and a depth of 5 to 7 feet. Because of themap scale, small areas of different soils may beincluded within the mapped areas of a specific soil.

The information is not site specific and does noteliminate the need for onsite investigation of the soilsor for testing and analysis by personnel experiencedin the design and construction of engineering works.

Government ordinances and regulations thatrestrict certain land uses or impose specific designcriteria were not considered in preparing theinformation in this section. Local ordinances andregulations should be considered in planning, in siteselection, and in design.

Soil properties, site features, and observedperformance were considered in determining theratings in this section. During the fieldwork for this soilsurvey, determinations were made about particle-sizedistribution, liquid limit, plasticity index, soil reaction,depth to bedrock, hardness of bedrock within 5 to7 feet of the surface, soil wetness, depth to a watertable, ponding, slope, likelihood of flooding, naturalsoil structure aggregation, and soil density. Data werecollected about kinds of clay minerals, mineralogy ofthe sand and silt fractions, and the kinds of adsorbedcations. Estimates were made for erodibility,permeability, corrosivity, shrink-swell potential,available water capacity, and other behavioralcharacteristics affecting engineering uses.

This information can be used to evaluate thepotential of areas for residential, commercial,industrial, and recreational uses; make preliminaryestimates of construction conditions; evaluatealternative routes for roads, streets, highways,pipelines, and underground cables; evaluatealternative sites for sanitary landfills, septic tankabsorption fields, and sewage lagoons; plan detailedonsite investigations of soils and geology; locatepotential sources of gravel, sand, earthfill, andtopsoil; plan drainage systems, irrigation systems,ponds, terraces, and other structures for soil andwater conservation; and predict performance ofproposed small structures and pavements bycomparing the performance of existing similarstructures on the same or similar soils.

Additional interpretations can be made using theinformation in the tables, along with soil maps, soildescriptions, and other data provided in this survey.

Some of the terms used in this soil survey have aspecial meaning in soil science and are defined in the“Glossary.”

Building Site DevelopmentSoil properties influence the development of

building sites, including the selection of the site, thedesign of the structure, construction, performanceafter construction, and maintenance. The “BuildingSite Development” tables show the degree and kindof soil limitations that affect dwellings with andwithout basements, small commercial buildings, localroads and streets, shallow excavations, and lawnsand landscaping.

The ratings in the tables are both verbal andnumerical. Rating class terms indicate the extent towhich the soils are limited by all of the soil featuresthat affect building site development. Not limitedindicates that the soil has features that are veryfavorable for the specified use. Good performanceand very low maintenance can be expected.Somewhat limited indicates that the soil has featuresthat are moderately favorable for the specified use.

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The limitations can be overcome or minimized byspecial planning, design, or installation. Fairperformance and moderate maintenance can beexpected. Very limited indicates that the soil has oneor more features that are unfavorable for the specifieduse. The limitations generally cannot be overcomewithout major soil reclamation, special design, orexpensive installation procedures. Poor performanceand high maintenance can be expected.

Numerical ratings in the tables indicate the severityof individual limitations. The ratings are shown asdecimal fractions ranging from 0.00 to 1.00. Theyindicate gradations between the point at which a soilfeature has the greatest negative impact on the use(1.00) and the point at which the soil feature is not alimitation (0.00).

Dwellings are single-family houses of three storiesor less. For dwellings without basements, thefoundation is assumed to consist of spread footingsof reinforced concrete built on undisturbed soil at adepth of 2 feet or at the depth of maximum frostpenetration, whichever is deeper. For dwellings withbasements, the foundation is assumed to consist ofspread footings of reinforced concrete built onundisturbed soil at a depth of about 7 feet. Theratings for dwellings are based on the soil propertiesthat affect the capacity of the soil to support a loadwithout movement and on the properties that affectexcavation and construction costs. The propertiesthat affect the load-supporting capacity include depthto a water table, ponding, flooding, subsidence, linearextensibility (shrink-swell potential), andcompressibility. Compressibility is inferred from theUnified classification. The properties that affect theease and amount of excavation include depth to awater table, ponding, flooding, slope, depth tobedrock or a cemented pan, hardness of bedrock ora cemented pan, and the amount and size of rockfragments.

Small commercial buildings are structures that areless than three stories high and do not havebasements. The foundation is assumed to consist ofspread footings of reinforced concrete built onundisturbed soil at a depth of 2 feet or at the depth ofmaximum frost penetration, whichever is deeper. Theratings are based on the soil properties that affect thecapacity of the soil to support a load withoutmovement and on the properties that affectexcavation and construction costs. The propertiesthat affect the load-supporting capacity include depthto a water table, ponding, flooding, subsidence, linearextensibility (shrink-swell potential), andcompressibility (which is inferred from the Unified

classification). The properties that affect the ease andamount of excavation include flooding, depth to awater table, ponding, slope, depth to bedrock or acemented pan, hardness of bedrock or a cementedpan, and the amount and size of rock fragments.

Local roads and streets have an all-weathersurface and carry automobile and light truck traffic allyear. They have a subgrade of cut or fill soil material;a base of gravel, crushed rock, or soil materialstabilized by lime or cement; and a surface of flexiblematerial (asphalt), rigid material (concrete), or gravelwith a binder. The ratings are based on the soilproperties that affect the ease of excavation andgrading and the traffic-supporting capacity. Theproperties that affect the ease of excavation andgrading are depth to bedrock or a cemented pan,hardness of bedrock or a cemented pan, depth to awater table, ponding, flooding, the amount of largestones, and slope. The properties that affect thetraffic-supporting capacity are soil strength (asinferred from the AASHTO group index number),subsidence, linear extensibility (shrink-swellpotential), the potential for frost action, depth to awater table, and ponding.

Shallow excavations are trenches or holes dug to amaximum depth of 5 or 6 feet for graves, utility lines,open ditches, or other purposes. The ratings arebased on the soil properties that influence the easeof digging and the resistance to sloughing. Depth tobedrock or a cemented pan, hardness of bedrock or acemented pan, the amount of large stones, anddense layers influence the ease of digging, filling, andcompacting. Depth to the seasonal high water table,flooding, and ponding may restrict the period whenexcavations can be made. Slope influences the easeof using machinery. Soil texture, depth to the watertable, and linear extensibility (shrink-swell potential)influence the resistance to sloughing.

Lawns and landscaping require soils on whichturf and ornamental trees and shrubs can beestablished and maintained. Irrigation is notconsidered in the ratings. The ratings are based onthe soil properties that affect plant growth andtrafficability after vegetation is established. Theproperties that affect plant growth are reaction;depth to a water table; ponding; depth to bedrockor a cemented pan; available water capacity in theupper 40 inches; content of salts, sodium, orcalcium carbonate; and sulfidic materials. Theproperties that affect trafficability are flooding; depthto a water table; ponding; slope; stoniness; and theamount of sand, clay, or organic matter in the surfacelayer.

Boundary County Area, Idaho—Part II 155

Sanitary FacilitiesThe “Sanitary Facilities” tables show the degree

and kind of soil limitations that affect septic tankabsorption fields, sewage lagoons, sanitary landfills,and daily cover for landfill. The ratings are both verbaland numerical. Rating class terms indicate the extentto which the soils are limited by all of the soil featuresthat affect these uses. Not limited indicates that thesoil has features that are very favorable for thespecified use. Good performance and very lowmaintenance can be expected. Somewhat limitedindicates that the soil has features that aremoderately favorable for the specified use. Thelimitations can be overcome or minimized by specialplanning, design, or installation. Fair performanceand moderate maintenance can be expected. Verylimited indicates that the soil has one or morefeatures that are unfavorable for the specified use.The limitations generally cannot be overcome withoutmajor soil reclamation, special design, or expensiveinstallation procedures. Poor performance and highmaintenance can be expected.

Numerical ratings in the tables indicate the severityof individual limitations. The ratings are shown asdecimal fractions ranging from 0.00 to 1.00. Theyindicate gradations between the point at which a soilfeature has the greatest negative impact on the use(1.00) and the point at which the soil feature is not alimitation (0.00).

Septic tank absorption fields are areas in whicheffluent from a septic tank is distributed into the soilthrough subsurface tiles or perforated pipe. Only thatpart of the soil between depths of 24 and 60 inches isevaluated. The ratings are based on the soilproperties that affect absorption of the effluent,construction and maintenance of the system, andpublic health. Permeability, depth to a water table,ponding, depth to bedrock or a cemented pan, andflooding affect absorption of the effluent. Stones andboulders, ice, and bedrock or a cemented paninterfere with installation. Subsidence interferes withinstallation and maintenance. Excessive slope maycause lateral seepage and surfacing of the effluent indownslope areas.

Some soils are underlain by loose sand and gravelor fractured bedrock at a depth of less than 4 feetbelow the distribution lines. In these soils theabsorption field may not adequately filter the effluent,particularly when the system is new. As a result, theground water may become contaminated.

Sewage lagoons are shallow ponds constructed tohold sewage while aerobic bacteria decompose the

solid and liquid wastes. Lagoons should have anearly level floor surrounded by cut slopes orembankments of compacted soil. Nearly impervioussoil material for the lagoon floor and sides is requiredto minimize seepage and contamination of groundwater. Considered in the ratings are slope,permeability, depth to a water table, ponding, depth tobedrock or a cemented pan, flooding, large stones,and content of organic matter.

Soil permeability is a critical property affecting thesuitability for sewage lagoons. Most porous soilseventually become sealed when they are used assites for sewage lagoons. Until sealing occurs,however, the hazard of pollution is severe. Soils thathave a permeability rate of more than 2 inches perhour are too porous for the proper functioning ofsewage lagoons. In these soils, seepage of theeffluent can result in contamination of the groundwater. Ground-water contamination is also a hazard iffractured bedrock is within a depth of 40 inches, if thewater table is high enough to raise the level ofsewage in the lagoon, or if floodwater overtops thelagoon.

A high content of organic matter is detrimental toproper functioning of the lagoon because it inhibitsaerobic activity. Slope, bedrock, and cemented panscan cause construction problems, and large stonescan hinder compaction of the lagoon floor. If thelagoon is to be uniformly deep throughout, the slopemust be gentle enough and the soil material must bethick enough over bedrock or a cemented pan tomake land smoothing practical.

A trench sanitary landfill is an area where solidwaste is placed in successive layers in an excavatedtrench. The waste is spread, compacted, and covereddaily with a thin layer of soil excavated at the site.When the trench is full, a final cover of soil material atleast 2-feet thick is placed over the landfill. Theratings in the tables are based on the soil propertiesthat affect the risk of pollution, the ease of excavation,trafficability, and revegetation. These propertiesinclude permeability, depth to bedrock or a cementedpan, depth to a water table, ponding, slope, flooding,texture, stones and boulders, highly organic layers,soil reaction, and content of salts and sodium. Unlessotherwise stated, the ratings apply only to that part ofthe soil within a depth of about 6 feet. For deepertrenches, onsite investigation may be needed.

Hard, nonrippable bedrock, creviced bedrock, orhighly permeable strata in or directly below theproposed trench bottom can affect the ease ofexcavation and the hazard of ground-water pollution.Slope affects construction of the trenches and the

156 Soil Survey

movement of surface water around the landfill. It alsoaffects the construction and performance of roads inareas of the landfill.

Soil texture and consistence affect the ease withwhich the trench is dug and the ease with which thesoil can be used as daily or final cover. Theydetermine the workability of the soil when dry andwhen wet. Soils that are plastic and sticky when wetare difficult to excavate, grade, or compact and aredifficult to place as a uniformly thick cover over alayer of refuse.

The soil material used as the final cover for atrench landfill should be suitable for plants. It shouldnot have excess sodium or salts and should not betoo acid. The surface layer generally has the bestworkability, the highest content of organic matter, andthe best potential for plants. Material from the surfacelayer should be stockpiled for use as the final cover.

In an area sanitary landfill, solid waste is placed insuccessive layers on the surface of the soil. Thewaste is spread, compacted, and covered daily with athin layer of soil from a source away from the site. Afinal cover of soil material at least 2-feet thick isplaced over the completed landfill. The ratings in thetables are based on the soil properties that affecttrafficability and the risk of pollution. These propertiesinclude flooding, permeability, depth to a water table,ponding, slope, and depth to bedrock or a cementedpan.

Flooding is a serious problem because it can resultin pollution in areas downstream from the landfill. Ifpermeability is too rapid or if fractured bedrock, afractured cemented pan, or the water table is close tothe surface, the leachate can contaminate the watersupply. Slope is a consideration because of the extragrading required to maintain roads in the steeperareas of the landfill. Also, leachate may flow along thesurface of the soils in the steeper areas and causedifficult seepage problems.

Daily cover for landfill is the soil material that isused to cover compacted solid waste in an areasanitary landfill. The soil material is obtained offsite,transported to the landfill, and spread over the waste.The ratings in the tables also apply to the final coverfor a landfill. They are based on the soil propertiesthat affect workability, the ease of digging, and theease of moving and spreading the material over therefuse daily during wet and dry periods. Theseproperties include soil texture; depth to a water table;ponding; rock fragments; slope; depth to bedrock or acemented pan; reaction; and content of salts, sodium,or lime.

Loamy or silty soils that are free of large stonesand 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 movingthe cover material. Also, it can influence runoff,erosion, and reclamation of the borrow area.

After soil material has been removed, the soilmaterial remaining in the borrow area must be thickenough over bedrock, a cemented pan, or the watertable to permit revegetation. The soil material used asthe final cover for a landfill should be suitable forplants. It should not have excess sodium, salts, orlime and should not be too acid.

Agricultural Waste ManagementSoil properties are important considerations in

areas where soils are used as sites for the treatmentand disposal of organic waste and wastewater.Selection of soils with properties that favor wastemanagement can help to prevent environmentaldamage.

The “Agricultural Waste Management” tables showthe degree and kind of soil limitations affecting thetreatment of agricultural waste, including municipaland food-processing wastewater and effluent fromlagoons or storage ponds. Municipal wastewater isthe waste stream from a municipality. It containsdomestic waste and may contain industrial waste. Itmay have received primary or secondary treatment. Itis rarely untreated sewage. Food-processingwastewater results from the preparation of fruits,vegetables, milk, cheese, and meats for publicconsumption. In places it is high in content of sodiumand chloride. In the context of these tables, theeffluent in lagoons and storage ponds is fromfacilities used to treat or store food-processingwastewater or domestic or animal waste. Domesticand food-processing wastewater is very dilute, andthe effluent from the facilities that treat or store itcommonly is very low in content of carbonaceous andnitrogenous material; the content of nitrogencommonly ranges from 10 to 30 milligrams perliter. The wastewater from animal waste treatmentlagoons or storage ponds, however, has muchhigher concentrations of these materials, mainlybecause the manure has not been diluted asmuch as the domestic waste. The content ofnitrogen in this wastewater generally ranges from50 to 2,000 milligrams per liter. When wastewater isapplied, checks should be made to ensure thatnitrogen, heavy metals, and salts are not added inexcessive amounts.

The ratings in the tables are for wastemanagement systems that not only dispose of and

Boundary County Area, Idaho—Part II 157

treat organic waste or wastewater but also arebeneficial to crops (application of manure and food-processing waste, application of sewage sludge, anddisposal of wastewater by irrigation) and for wastemanagement systems that are designed only for thepurpose of wastewater disposal and treatment(overland flow of wastewater, rapid infiltration ofwastewater, and slow rate treatment of wastewater).

The ratings are both verbal and numerical. Ratingclass terms indicate the extent to which the soils arelimited by all of the soil features that affect agriculturalwaste management. Not limited indicates that the soilhas features that are very favorable for the specifieduse. Good performance and very low maintenancecan be expected. Somewhat limited indicates that thesoil has features that are moderately favorable for thespecified use. The limitations can be overcome orminimized by special planning, design, or installation.Fair performance and moderate maintenance can beexpected. Very limited indicates that the soil has oneor more features that are unfavorable for the specifieduse. The limitations generally cannot be overcomewithout major soil reclamation, special design, orexpensive installation procedures. Poor performanceand high maintenance can be expected.

Numerical ratings in the tables indicate the severityof individual limitations. The ratings are shown asdecimal fractions ranging from 0.01 to 1.00. Theyindicate gradations between the point at which a soilfeature has the greatest negative impact on the use(1.00) and the point at which the soil feature is not alimitation (0.00).

Application of manure and food-processing wastenot only disposes of waste material but also canimprove crop production by increasing the supply ofnutrients in the soils where the material is applied.Manure is the excrement of livestock and poultry, andfood-processing waste is damaged fruit andvegetables and the peelings, stems, leaves, pits, andsoil particles removed in food preparation. Themanure and food-processing waste are either solid,slurry, or liquid. Their nitrogen content varies. A highcontent of nitrogen limits the application rate. Toxic orotherwise dangerous wastes, such as those mixedwith the lye used in food processing, are notconsidered in the ratings.

The ratings are based on the soil properties thataffect absorption, plant growth, microbial activity,erodibility, the rate at which the waste is applied, andthe method by which the waste is applied. Theproperties that affect absorption include permeability,depth to a water table, ponding, the sodiumadsorption ratio, depth to bedrock or a cemented pan,and available water capacity. The properties that

affect plant growth and microbial activity includereaction, the sodium adsorption ratio, salinity, andbulk density. The wind erodibility group, the soilerodibility factor K, and slope are considered inestimating the likelihood that wind erosion or watererosion will transport the waste material from theapplication site. Stones, cobbles, a water table,ponding, and flooding can hinder the application ofwaste. Permanently frozen soils are unsuitable forwaste treatment.

Application of sewage sludge not only disposes ofwaste material but also can improve crop productionby increasing the supply of nutrients in the soilswhere the material is applied. In the context of thistable, sewage sludge is the residual product of thetreatment of municipal sewage. The solid componentconsists mainly of cell mass, primarily bacteria cellsthat developed during secondary treatment and haveincorporated soluble organics into their own bodies.The sludge has small amounts of sand, silt, and othersolid debris. The content of nitrogen varies. Somesludge has constituents that are toxic to plants orhazardous to the food chain, such as heavy metalsand exotic organic compounds, and should beanalyzed chemically prior to use.

The content of water in the sludge ranges fromabout 98 percent to less than 40 percent. The sludgeis considered liquid if it is more than about 90 percentwater, slurry if it is about 50 to 90 percent water, andsolid if it is less than about 50 percent water.

The ratings in the table are based on the soilproperties that affect absorption, plant growth,microbial activity, erodibility, the rate at which thesludge is applied, and the method by which thesludge is applied. The properties that affectabsorption, plant growth, and microbial activityinclude permeability, depth to a water table, ponding,the sodium adsorption ratio, depth to bedrock or acemented pan, available water capacity, reaction,salinity, and bulk density. The wind erodibility group,the soil erodibility factor K, and slope are consideredin estimating the likelihood that wind erosion or watererosion will transport the waste material from theapplication site. Stones, cobbles, a water table,ponding, and flooding can hinder the application ofsludge. Permanently frozen soils are unsuitable forwaste treatment.

Disposal of wastewater by irrigation not onlydisposes of municipal wastewater and wastewaterfrom food-processing plants, lagoons, and storageponds but also can improve crop production byincreasing the amount of water available to crops.The ratings in the table are based on the soilproperties that affect the design, construction,

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management, and performance of the irrigationsystem. The properties that affect design andmanagement include the sodium adsorption ratio,depth to a water table, ponding, available watercapacity, permeability, slope, and flooding. Theproperties that affect construction include stones,cobbles, depth to bedrock or a cemented pan, depthto a water table, and ponding. The properties thataffect performance include depth to bedrock or acemented pan, bulk density, the sodium adsorptionratio, salinity, reaction, and the cation-exchangecapacity, which is used to estimate the capacity of asoil to adsorb heavy metals. Permanently frozen soilsare not suitable for disposal of wastewater byirrigation.

Overland flow of wastewater is a process in whichwastewater is applied to the upper reaches of slopedland and allowed to flow across vegetated surfaces,sometimes called terraces, to runoff-collectionditches. The length of the run generally is 150 to300 feet. The application rate ranges from 2.5 to16.0 inches per week. It commonly exceeds the rateneeded for irrigation of cropland. The wastewaterleaves solids and nutrients on the vegetated surfacesas it flows downslope in a thin film. Most of the waterreaches the collection ditch, some is lost throughevapotranspiration, and a small amount maypercolate to the ground water.

The ratings in the table are based on the soilproperties that affect absorption, plant growth,microbial activity, and the design and construction ofthe system. Reaction and the cation-exchangecapacity affect absorption. Reaction, salinity, and thesodium adsorption ratio affect plant growth andmicrobial activity. Slope, permeability, depth to awater table, ponding, flooding, depth to bedrock or acemented pan, stones, and cobbles affect design andconstruction. Permanently frozen soils are unsuitablefor waste treatment.

Rapid infiltration of wastewater is a process inwhich wastewater applied in a level basin at a rate of4 to 120 inches per week percolates through the soil.The wastewater may eventually reach the groundwater. The application rate commonly exceeds therate needed for irrigation of cropland. Vegetation isnot a necessary part of the treatment; hence, thebasins may or may not be vegetated. The thickness ofthe soil material needed for proper treatment of thewastewater is more than 72 inches. As a result,geologic and hydrologic investigation is needed toensure proper design and performance and todetermine the risk of ground-water pollution.

The ratings in the table are based on the soilproperties that affect the risk of pollution and the

design, construction, and performance of the system.Depth to a water table, ponding, flooding, and depthto bedrock or a cemented pan affect the risk ofpollution and the design and construction of thesystem. Slope, stones, and cobbles also affect designand construction. Permeability and reaction affectperformance. Permanently frozen soils are unsuitablefor waste treatment.

Slow rate treatment of wastewater is a process inwhich wastewater is applied to land at a rate normallybetween 0.5 inch and 4.0 inches per week. Theapplication rate commonly exceeds the rate neededfor irrigation of cropland. The applied wastewater istreated as it moves through the soil. Much of thetreated water may percolate to the ground water,and some enters the atmosphere throughevapotranspiration. The applied water generally isnot allowed to run off the surface. Waterlogging isprevented either through control of the applicationrate or through the use of tile drains, or both.

The ratings in the table are based on the soilproperties that affect absorption, plant growth,microbial activity, erodibility, and the application ofwaste. The properties that affect absorption includethe sodium adsorption ratio, depth to a water table,ponding, available water capacity, permeability, depthto bedrock or a cemented pan, reaction, the cation-exchange capacity, and slope. Reaction, the sodiumadsorption ratio, salinity, and bulk density affect plantgrowth and microbial activity. The wind erodibilitygroup, the soil erodibility factor K, and slope areconsidered in estimating the likelihood of winderosion or water erosion. Stones, cobbles, a watertable, ponding, and flooding can hinder theapplication of waste. Permanently frozen soils areunsuitable for waste treatment.

Construction MaterialsThe “Construction Materials” tables give

information about the soils as potential sources ofgravel, sand, topsoil, reclamation material, androadfill. Normal compaction, minor processing, andother standard construction practices are assumed.

The soils are rated good, fair, or poor as potentialsources of topsoil, reclamation material, and roadfill.The features that limit the soils as sources of thesematerials are specified in the tables. The numericalratings given after the specified features indicate thedegree to which the features limit the soils as sourcesof topsoil, reclamation material, or roadfill—the lowerthe number, the greater the limitation. The soils arerated as a probable or improbable source of sandand gravel. A rating of probable means that the

Boundary County Area, Idaho—Part II 159

source material is likely to be in or below the soil. Thenumerical ratings in these columns indicate thedegree of probability. The number 0.00 indicates thatthe soil is an improbable source. A number between0.00 and 1.00 indicates the degree to which the soilis a probable source of sand or gravel.

Gravel and sand are natural aggregates suitablefor commercial use with a minimum of processing.They are used in many kinds of construction.Specifications for each use vary widely. In the first“Construction Materials” table, only the probability offinding material in suitable quantity is evaluated. Thesuitability of the material for specific purposes is notevaluated, nor are factors that affect excavation of thematerial. The properties used to evaluate the soil as asource of gravel or sand are gradation of grain sizes(as indicated by the Unified classification of the soil),the thickness of suitable material, and the content ofrock fragments. If the lowest layer of the soil containsgravel or sand, the soil is rated as a probable sourceregardless of thickness. The assumption is that thegravel or sand layer below the depth of observationexceeds the minimum thickness.

Reclamation material is used in areas that havebeen drastically disturbed by surface mining orsimilar activities. When these areas are reclaimed,layers of soil material or unconsolidated geologicalmaterial, or both, are replaced in a vertical sequence.The reconstructed soil favors plant growth. Theratings in the tables do not apply to quarries andother mined areas that require an offsite source ofreconstruction material. The ratings are based on thesoil properties that affect erosion and stability of thesurface and the productive potential of thereconstructed soil. These properties include thecontent of sodium, salts, and calcium carbonate;reaction; available water capacity; erodibility; texture;content of rock fragments; and content of organicmatter and other features that affect fertility.

Roadfill is soil material that is excavated in oneplace and used in road embankments in anotherplace. In these tables, the soils are rated as a sourceof roadfill for low embankments, generally less than6-feet high and less exacting in design than higherembankments.

The ratings are for the whole soil, from the surfaceto a depth of about 5 feet. It is assumed that soillayers will be mixed when the soil material isexcavated and spread.

The ratings are based on the amount of suitablematerial and on soil properties that affect the ease ofexcavation and the performance of the material afterit is in place. The thickness of the suitable material isa major consideration. The ease of excavation is

affected by large stones, depth to a water table, andslope. How well the soil performs in place after it hasbeen compacted and drained is determined by itsstrength (as inferred from the AASHTO classificationof the soil) and linear extensibility (shrink-swellpotential).

Topsoil is used to cover an area so that vegetationcan be established and maintained. The upper40 inches of a soil is evaluated for use as topsoil.Also evaluated is the reclamation potential of theborrow area. The ratings are based on the soilproperties that affect plant growth; the ease ofexcavating, loading, and spreading the material; andreclamation of the borrow area. Toxic substances, soilreaction, and the properties that are inferred from soiltexture, 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 ofsuitable material. Reclamation of the borrow area isaffected by slope, depth to a water table, rockfragments, depth to bedrock or a cemented pan, andtoxic material.

The surface layer of most soils is generallypreferred for topsoil because of its organic mattercontent. Organic matter greatly increases theabsorption and retention of moisture and nutrients forplant growth.

Water ManagementThe “Water Management” tables give information

on the soil properties and site features that affectwater management. The degree and kind of soillimitations are given for pond reservoir areas;embankments, dikes, and levees; and aquifer-fedexcavated ponds. The limitations are consideredslight if soil properties and site features are generallyfavorable for the indicated use and limitations areminor and are easily overcome; moderate if soilproperties or site features are not favorable for theindicated use and special planning, design, ormaintenance is needed to overcome or minimize thelimitations; and severe if soil properties or sitefeatures are so unfavorable or so difficult to overcomethat special design, significant increase inconstruction costs, and possibly increasedmaintenance are required.

These tables also give for each soil the restrictivefeatures that affect drainage, irrigation, terraces anddiversions, and grassed waterways.

Pond reservoir areas hold water behind a dam orembankment. Soils best suited to this use have lowseepage potential in the upper 60 inches. The

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seepage potential is determined by the permeabilityof the soil and the depth to fractured bedrock or otherpermeable material. Excessive slope can affect thestorage capacity of the reservoir area.

Embankments, dikes, and levees are raisedstructures of soil material, generally less than 20-feethigh, constructed to impound water or to protect landagainst overflow. In these tables, the soils are ratedas a source of material for embankment fill. Theratings apply to the soil material below the surfacelayer to a depth of about 5 feet. It is assumed that soillayers will be uniformly mixed and compacted duringconstruction.

The ratings do not indicate the ability of thenatural soil to support an embankment. Soilproperties to a depth even greater than the heightof the embankment can affect performance andsafety of the embankment. Generally, deeperonsite investigation is needed to determine theseproperties.

Soil material in embankments must be resistantto seepage, piping, and erosion and have favorablecompaction characteristics. Unfavorable featuresinclude less than 5 feet of suitable material and ahigh content of stones or boulders, organic matter,or salts or sodium. A high water table affects theamount of usable material. It also affects trafficability.

Aquifer-fed excavated ponds are pits or dugoutsthat extend to a ground-water aquifer or to a depthbelow a permanent water table. Excluded are pondsthat are fed only by surface runoff and embankmentponds that impound water 3 feet or more above theoriginal surface. Excavated ponds are affected bydepth to a permanent water table, permeability of theaquifer, and quality of the water as inferred from thesalinity of the soil. Depth to bedrock and the contentof large stones affect the ease of excavation.

Drainage is the removal of excess surface andsubsurface water from the soil. How easily andeffectively the soil is drained depends on the depth tobedrock, a cemented pan, or other layers that affectthe rate of water movement; permeability; depth to a

high water table or depth of standing water if the soilis subject to ponding; slope; susceptibility to flooding;subsidence of organic layers; and the potential forfrost action. Excavating and grading and the stabilityof ditchbanks are affected by depth to bedrock or acemented pan, large stones, slope, and the hazard ofcutbanks caving. The productivity of the soil afterdrainage is adversely affected by extreme acidity orby toxic substances in the root zone, such as salts,sodium, and sulfur. Availability of drainage outlets isnot considered in the ratings.

Irrigation is the controlled application of water tosupplement rainfall and support plant growth. Thedesign and management of an irrigation system areaffected by depth to the water table, the need fordrainage, flooding, available water capacity, intakerate, permeability, erosion hazard, and slope. Theconstruction of a system is affected by large stonesand depth to bedrock or a cemented pan. Theperformance of a system is affected by the depth ofthe root zone, the amount of salts or sodium, and soilreaction.

Terraces and diversions are embankments or acombination of channels and ridges constructedacross a slope to control erosion and conservemoisture by intercepting runoff. Slope, wetness, largestones, and depth to bedrock or a cemented panaffect the construction of terraces and diversions. Arestricted rooting depth, a severe hazard of winderosion or water erosion, an excessively coarsetexture, and restricted permeability adversely affectmaintenance.

Grassed waterways are natural or constructedchannels, generally broad and shallow, that conductsurface water to outlets at a nonerosive velocity.Large stones, wetness, slope, and depth to bedrockor a cemented pan affect the construction of grassedwaterways. A hazard of wind erosion, low availablewater capacity, restricted rooting depth, toxicsubstances such as salts and sodium, and restrictedpermeability adversely affect the growth andmaintenance of the grass after construction.

299

Soil Properties

Data relating to soil properties are collected duringthe course of the soil survey. Data and estimates ofsoil and water features, listed in the tables, areexplained on the following pages.

Soil properties are ascertained by fieldexamination of the soils and by laboratory indextesting of some benchmark soils. Establishedstandard procedures are followed. During the survey,many shallow borings are made and examined toidentify and classify the soils and to delineate themon the soil maps. Samples are taken from sometypical profiles and tested in the laboratory todetermine particle-size distribution, plasticity, andcompaction characteristics.

Estimates of soil properties are based on fieldexaminations, on laboratory tests of samples from thesurvey area, and on laboratory tests of samples ofsimilar soils in nearby areas. Tests verify fieldobservations, verify properties that cannot beestimated accurately by field observation, and help tocharacterize key soils.

Estimates of soil properties shown in the tablesinclude the range of grain-size distribution andAtterberg limits, the engineering classification, andthe physical and chemical properties of the majorlayers of each soil. Pertinent soil and water featuresalso are given.

Engineering Index PropertiesThe “Engineering Index Properties” table gives the

engineering classifications and the range of indexproperties for the layers of each soil in the surveyarea.

Depth to the upper and lower boundaries of eachlayer is indicated.

Texture is given in the standard terms used by theU.S. Department of Agriculture. These terms aredefined according to percentages of sand, silt, andclay in the fraction of the soil that is less than 2millimeters in diameter. “Loam,” for example, is soilthat is 7 to 27 percent clay, 28 to 50 percent silt, andless than 52 percent sand. If the content of particlescoarser than sand is 15 percent or more, an

appropriate modifier is added, for example, “gravelly.”Textural terms are defined in the “Glossary.”

Classification of the soils is determined accordingto the Unified soil classification system (ASTM, 1998)and the system adopted by the American Associationof State Highway and Transportation Officials(AASHTO, 1998).

The Unified system classifies soils according toproperties that affect their use as constructionmaterial (Portland Cement Association, 1973). Soilsare classified according to particle-size distribution ofthe fraction less than 3 inches in diameter andaccording to plasticity index, liquid limit, and organicmatter content. Sandy and gravelly soils are identifiedas GW, GP, GM, GC, SW, SP, SM, and SC; silty andclayey soils as ML, CL, OL, MH, CH, and OH; andhighly organic soils as PT. Soils exhibitingengineering properties of two groups can have a dualclassification, for example, CL-ML.

The AASHTO system classifies soils according tothose properties that affect roadway construction andmaintenance. In this system, the fraction of a mineralsoil that is less than 3 inches in diameter is classifiedin one of seven groups from A-1 through A-7 on thebasis of particle-size distribution, liquid limit, andplasticity index. Soils in group A-1 are coarse grainedand low in content of fines (silt and clay). At the otherextreme, soils in group A-7 are fine grained. Highlyorganic soils are classified in group A-8 on the basisof visual inspection.

If laboratory data are available, the A-1, A-2, andA-7 groups are further classified as A-1-a, A-1-b,A-2-4, A-2-5, A-2-6, A-2-7, A-7-5, or A-7-6. As anadditional refinement, the suitability of a soil assubgrade material can be indicated by a group indexnumber. Group index numbers range from 0 for thebest subgrade material to 20 or higher for thepoorest.

Rock fragments larger than 10 inches in diameterand 3 to 10 inches in diameter are indicated as apercentage of the total soil on a dry-weight basis. Thepercentages are estimates determined mainly byconverting volume percentage in the field to weightpercentage.

300 Soil Survey

Percentage (of soil particles) passing designatedsieves is the percentage of the soil fraction less than3 inches in diameter based on an ovendry weight.The sieves, numbers 4, 10, 40, and 200 (USAStandard Series), have openings of 4.76, 2.00, 0.420,and 0.074 millimeters, respectively. Estimates arebased on laboratory tests of soils sampled in thesurvey area and in nearby areas and on estimatesmade in the field.

Liquid limit and plasticity index (Atterberg limits)indicate the plasticity characteristics of a soil. Theestimates are based on test data from the surveyarea or from nearby areas and on field examination.

The estimates of particle-size distribution, liquidlimit, and plasticity index are generally rounded to thenearest 5 percent. Thus, if the ranges of gradationand Atterberg limits extend a marginal amount (1 or2 percentage points) across classificationboundaries, the classification in the marginal zone isgenerally omitted in the table.

Physical PropertiesThe “Physical Properties of the Soils” table shows

estimates of some physical characteristics andfeatures that affect soil behavior. These estimates aregiven for the layers of each soil in the survey area.The estimates are based on field observations andon test data for these and similar soils.

Depth to the upper and lower boundaries of eachlayer is indicated.

Particle size is the effective diameter of a soilparticle as measured by sedimentation, sieving, ormicrometric methods. Particle sizes are expressed asclasses with specific effective diameter class limits.The broad classes are sand, silt, and clay, rangingfrom the larger to the smaller.

Sand as a soil separate consists of mineral soilparticles that are 0.05 millimeter to 2 millimeters indiameter. Silt as a soil separate consists of mineralsoil particles that are 0.002 to 0.05 millimeter indiameter. Clay as a soil separate consists of mineralsoil particles that are less than 0.002 millimeter indiameter. In the “Physical Properties of the Soils”table, the estimated clay content of each soil layer isgiven as a percentage, by weight, of the soil materialthat is less than 2 millimeters in diameter.

The content of sand, silt, and clay affects thephysical behavior of a soil. Particle size is importantfor engineering and agronomic interpretations, fordetermination of soil hydrologic qualities, and for soilclassification.

The amount and kind of clay affect the fertility andphysical condition of the soil and the ability of the soil

to adsorb cations and to retain moisture. Theyinfluence shrink-swell potential, permeability,plasticity, the ease of soil dispersion, and other soilproperties. The amount and kind of clay in a soil alsoaffect tillage and earthmoving operations.

Moist bulk density is the weight of soil (ovendry)per unit volume. Volume is measured when the soilis at field moisture capacity, that is, the moisturecontent at 1/3- or 1/10-bar (33kPa or 10kPa) moisturetension. Weight is determined after the soil is dried at105 degrees C. In the table, the estimated moist bulkdensity of each soil horizon is expressed in gramsper cubic centimeter of soil material that is less than2 millimeters in diameter. Bulk density data are usedto compute shrink-swell potential, available watercapacity, total pore space, and other soil properties.The moist bulk density of a soil indicates the porespace available for water and roots. Depending onsoil texture, a bulk density of more than 1.4 canrestrict water storage and root penetration. Moist bulkdensity is influenced by texture, kind of clay, contentof organic matter, and soil structure.

Permeability (Ksat

) refers to the ability of a soil totransmit water or air. The term “permeability,” as usedin soil surveys, indicates saturated hydraulicconductivity (K

sat). The estimates in the table indicate

the rate of water movement, in inches per hour, whenthe soil is saturated. They are based on soilcharacteristics observed in the field, particularlystructure, porosity, and texture. Permeability isconsidered in the design of soil drainage systemsand septic tank absorption fields.

Available water capacity refers to the quantity ofwater that the soil is capable of storing for use byplants. The capacity for water storage is given ininches of water per inch of soil for each soil layer. Thecapacity varies, depending on soil properties thataffect retention of water. The most importantproperties are the content of organic matter, soiltexture, bulk density, and soil structure. Availablewater capacity is an important factor in the choice ofplants or crops to be grown and in the design andmanagement of irrigation systems. Available watercapacity is not an estimate of the quantity of wateractually available to plants at any given time.

Linear extensibility refers to the change in length ofan unconfined clod as moisture content is decreasedfrom a moist to a dry state. It is an expression of thevolume change between the water content of the clodat 1/3- or 1/10-bar tension (33kPa or 10kPa tension)and oven dryness. The volume change is reported inthe table as percent change for the whole soil.Volume change is influenced by the amount and typeof clay minerals in the soil.

Boundary County Area, Idaho—Part II 301

Linear extensibility is used to determine the shrink-swell potential of soils. The shrink-swell potential islow if the soil has a linear extensibility of less than3 percent, moderate if 3 to 6 percent, high if 6 to9 percent, and very high if more than 9 percent. If thelinear extensibility is more than 3, shrinking andswelling can cause damage to buildings, roads, andother structures and to plant roots. Special designcommonly is needed.

Organic matter is the plant and animal residue inthe soil at various stages of decomposition. In the“Physical Properties of the Soils” table, the estimatedcontent of organic matter is expressed as apercentage, by weight, of the soil material that is lessthan 2 millimeters in diameter.

The content of organic matter in a soil can bemaintained by returning crop residue to the soil.Organic matter has a positive effect on availablewater capacity, water infiltration, soil organismactivity, and tilth. It is a source of nitrogen and othernutrients for crops and soil organisms.

Erosion factors are shown in the “PhysicalProperties of the Soils” table as the K factor (Kw andKf) and the T factor. Erosion factor K indicates thesusceptibility of a soil to sheet and rill erosion bywater. Factor K is one of several factors used in theUniversal Soil Loss Equation (USLE) and theRevised Universal Soil Loss Equation (RUSLE) topredict the average annual rate of soil loss by sheetand rill erosion in tons per acre per year. Theestimates are based primarily on percentage of silt,sand, and organic matter and on soil structure andpermeability. Values of K range from 0.02 to 0.69.Other factors being equal, the higher the value, themore susceptible the soil is to sheet and rill erosionby water.

Erosion factor Kw indicates the erodibility of thewhole soil. The estimates are modified by thepresence of rock fragments.

Erosion factor Kf indicates the erodibility ofthe fine-earth fraction, or the material less than2 millimeters in size.

Erosion factor T is an estimate of the maximumaverage annual rate of soil erosion by wind or waterthat can occur without affecting crop productivity overa sustained period. The rate is in tons per acre peryear.

Wind erodibility groups are made up of soils thathave similar properties affecting their susceptibility towind erosion in cultivated areas. The soils assignedto group 1 are the most susceptible to wind erosion,and those assigned to group 8 are the leastsusceptible. The groups are as follows:

1. Coarse sands, sands, fine sands, and veryfine sands.

2. Loamy coarse sands, loamy sands, loamyfine sands, loamy very fine sands, ashmaterial, and sapric soil material.

3. Coarse sandy loams, sandy loams, finesandy loams, and very fine sandy loams.

4L. Calcareous loams, silt loams, clay loams,and silty clay loams.

4. Clays, silty clays, noncalcareous clayloams, and silty clay loams that are morethan 35 percent clay.

5. Noncalcareous loams and silt loams thatare less than 20 percent clay and sandyclay loams, sandy clays, and hemic soilmaterial.

6. Noncalcareous loams and silt loams thatare more than 20 percent clay andnoncalcareous clay loams that are lessthan 35 percent clay.

7. Silts, noncalcareous silty clay loams thatare less than 35 percent clay, and fibric soilmaterial.

8. Soils that are not subject to wind erosionbecause of coarse fragments on thesurface or because of surface wetness.

Wind erodibility index is a numerical valueindicating the susceptibility of soil to wind erosion, orthe tons per acre per year that can be expected to belost to wind erosion. There is a close correlationbetween wind erosion and the texture of the surfacelayer, the size and durability of surface clods, rockfragments, organic matter, and a calcareous reaction.Soil moisture and frozen soil layers also influencewind erosion.

Chemical PropertiesThe “Chemical Properties of the Soils” table shows

estimates of some chemical characteristics andfeatures that affect soil behavior. These estimates aregiven for the layers of each soil in the survey area.The estimates are based on field observations andon test data for these and similar soils.

Depth to the upper and lower boundaries of eachlayer is indicated.

Cation-exchange capacity is the total amount ofextractable bases that can be held by the soil,expressed in terms of milliequivalents per 100 gramsof soil at neutrality (pH 7.0) or at some other statedpH value. Soils having a low cation-exchangecapacity hold fewer cations and may require more

302 Soil Survey

frequent applications of fertilizer than soils having ahigh cation-exchange capacity. The ability to retaincations reduces the hazard of ground-water pollution.

Effective cation-exchange capacity refers to thesum of extractable bases plus aluminum expressed interms of milliequivalents per 100 grams of soil. It isdetermined for soils that have pH of less than 5.5.

Soil reaction is a measure of acidity or alkalinity.The pH of each soil horizon is based on many fieldtests. For many soils, values have been verified bylaboratory analyses. Soil reaction is important inselecting crops and other plants, in evaluating soilamendments for fertility and stabilization, and indetermining the risk of corrosion.

Calcium carbonate equivalent is the percent ofcarbonates, by weight, in the fraction of the soil lessthan 2 millimeters in size. The availability of plantnutrients is influenced by the amount of carbonates inthe soil. Incorporating nitrogen fertilizer intocalcareous soils helps to prevent nitrite accumulationand ammonium-N volatilization.

Gypsum is expressed as a percent, by weight, ofhydrated calcium sulfates in the fraction of the soilless than 20 millimeters in size. Gypsum is partiallysoluble in water. Soils that have a high content ofgypsum may collapse if the gypsum is removed bypercolating water.

Salinity is a measure of soluble salts in the soil atsaturation. It is expressed as the electricalconductivity of the saturation extract, in millimhos percentimeter at 25 degrees C. Estimates are based onfield and laboratory measurements at representativesites of nonirrigated soils. The salinity of irrigatedsoils is affected by the quality of the irrigation waterand by the frequency of water application. Hence, thesalinity of soils in individual fields can differ greatlyfrom the value given in the table. Salinity affects thesuitability of a soil for crop production, the stability ofsoil if used as construction material, and the potentialof the soil to corrode metal and concrete.

Sodium adsorption ratio (SAR) is a measure of theamount of sodium (Na) relative to calcium (Ca) andmagnesium (Mg) in the water extract from saturatedsoil paste. It is the ratio of the Na concentrationdivided by the square root of one-half of the Ca + Mgconcentration. Soils that have SAR values of 13 ormore may be characterized by an increaseddispersion of organic matter and clay particles,reduced permeability and aeration, and a generaldegradation of soil structure.

Water FeaturesThe “Water Features” table gives estimates of

various water features. The estimates are used inland use planning that involves engineeringconsiderations.

Hydrologic soil groups are based on estimates ofrunoff potential. Soils are assigned to one of fourgroups according to the rate of water infiltration whenthe soils are not protected by vegetation, arethoroughly wet, and receive precipitation from long-duration storms.

The four hydrologic soil groups are:

Group A. Soils having a high infiltration rate (lowrunoff potential) when thoroughly wet. Mainlydeep, well-drained to excessively drained sandsor gravelly sands. These soils have a high rate ofwater transmission.

Group B. Soils having a moderate infiltration ratewhen thoroughly wet. Chiefly moderately deep ordeep, moderately well-drained or well-drainedsoils that have moderately fine texture tomoderately coarse texture. These soils have amoderate rate of water transmission.

Group C. Soils having a slow infiltration rate whenthoroughly wet. Chiefly, soils having a layer thatimpedes the downward movement of water orsoils of moderately fine texture or fine texture.These soils have a slow rate of watertransmission.

Group D. Soils having a very slow infiltration rate(high runoff potential) when thoroughly wet.Chiefly, clays that have a high shrink-swellpotential, soils that have a high water table, soilsthat have a claypan or clay layer at or near thesurface, and soils that are shallow over nearlyimpervious material. These soils have a very slowrate of water transmission.

If a soil is assigned to a dual hydrologic group(A/D, B/D, or C/D), the first letter is for drained areasand the second is for undrained areas.

The month column in the table indicates theportion of the year in which the feature is most likelyto be a concern.

Water table refers to a saturated zone in the soil.The “Water Features” table indicates, by month, depthto the top (upper limit) and base (lower limit) of thesaturated zone in most years. Estimates of the upperand lower limits are based mainly on observations of

Boundary County Area, Idaho—Part II 303

the water table at selected sites and on evidence of asaturated zone, namely grayish colors or mottles(redox features) in the soil. A saturated zone thatlasts for less than a month is not considered a watertable.

Ponding is standing water in a closed depression.Unless a drainage system is installed, the water isremoved only by percolation, transpiration, orevaporation. Frequency is expressed as none, rare,occasional, and frequent. None means that pondingis not probable; rare that it is unlikely but possibleunder unusual weather conditions (the chance ofponding is nearly 0 percent to 5 percent in any year);occasional that it occurs, on the average, once orless in 2 years (the chance of ponding is 5 to 50percent in any year); and frequent that it occurs, onthe average, more than once in 2 years (the chanceof ponding is more than 50 percent in any year).

Flooding is the temporary inundation of an areacaused by overflowing streams, by runoff fromadjacent slopes, or by tides. Water standing for shortperiods after rainfall or snowmelt is not consideredflooding, and water standing in swamps and marshesis considered ponding rather than flooding.

Duration and frequency are estimated. Duration isexpressed as extremely brief if 0.1 hour to 4 hours,very brief if 4 hours to 2 days, brief if 2 to 7 days, longif 7 to 30 days, and very long if more than 30 days.Frequency is expressed as none, very rare, rare,occasional, frequent, and very frequent. None meansthat flooding is not probable; very rare that it is veryunlikely but possible under extremely unusualweather conditions (the chance of flooding is lessthan 1 percent in any year); rare that it is unlikely butpossible under unusual weather conditions (thechance of flooding is 1 to 5 percent in any year);occasional that it occurs infrequently under normalweather conditions (the chance of flooding is 5 to50 percent in any year); frequent that it is likely tooccur often under normal weather conditions (thechance of flooding is more than 50 percent in anyyear but is less than 50 percent in all months in anyyear); and very frequent that it is likely to occur veryoften under normal weather conditions (the chance offlooding is more than 50 percent in all months of anyyear).

The information is based on evidence in the soilprofile, namely thin strata of gravel, sand, silt, or claydeposited by floodwater; irregular decrease inorganic matter content with increasing depth; andlittle or no horizon development.

Also considered is local information about theextent and levels of flooding and the relation of eachsoil on the landscape to historic floods. Information

on the extent of flooding based on soil data is lessspecific than that provided by detailed engineeringsurveys that delineate flood-prone areas at specificflood frequency levels.

Soil FeaturesThe “Soil Features” table gives estimates of

various soil features. The estimates are used in landuse planning that involves engineeringconsiderations.

A restrictive layer is a nearly continuous layer thathas one or more physical, chemical, or thermalproperties that significantly impede the movement ofwater and air through the soil or that restrict roots orotherwise provide an unfavorable root environment.Examples are bedrock, cemented layers, denselayers, and frozen layers. The table indicates thethickness and hardness of the restrictive layer, bothof which significantly affect the ease of excavation.Depth to top is the vertical distance from the soilsurface to the upper boundary of the restrictive layer.

Subsidence is the settlement of organic soils or ofsaturated mineral soils of very low density.Subsidence generally results from either desiccationand shrinkage or oxidation of organic material, orboth, following drainage. Subsidence takes placegradually, usually over a period of several years. Thetable shows the expected initial subsidence, whichusually is a result of drainage, and total subsidence,which results from a combination of factors.

Potential for frost action is the likelihood of upwardor lateral expansion of the soil caused by theformation of segregated ice lenses (frost heave) andthe subsequent collapse of the soil and loss ofstrength on thawing. Frost action occurs whenmoisture moves into the freezing zone of the soil.Temperature, texture, density, permeability, content oforganic matter, and depth to the water table are themost important factors considered in evaluating thepotential for frost action. It is assumed that the soil isnot insulated by vegetation or snow and is notartificially drained. Silty and highly structured, clayeysoils that have a high water table in winter are themost susceptible to frost action. Well drained, verygravelly, or very sandy soils are the least susceptible.Frost heave and low soil strength during thawingcause damage to pavements and other rigidstructures.

Risk of corrosion pertains to potential soil-inducedelectrochemical or chemical action that corrodes orweakens uncoated steel or concrete. The rate ofcorrosion of uncoated steel is related to such factorsas soil moisture, particle-size distribution, acidity, and

304 Soil Survey

electrical conductivity of the soil. The rate of corrosionof concrete is based mainly on the sulfate andsodium content, texture, moisture content, and acidityof the soil. Special site examination and design maybe needed if the combination of factors results in asevere hazard of corrosion. The steel or concrete ininstallations that intersect soil boundaries or soillayers is more susceptible to corrosion than the steelor concrete in installations that are entirely within onekind of soil or within one soil layer.

For uncoated steel, the risk of corrosion,expressed as low, moderate, or high, is based on soildrainage class, total acidity, electrical resistivity nearfield capacity, and electrical conductivity of thesaturation extract.

For concrete, the risk of corrosion also isexpressed as low, moderate, or high. It is based onsoil texture, acidity, and amount of sulfates in thesaturation extract.

439

References

Aadland, R.K., and E.H. Bennett. 1979. Geologic map of the Sandpoint quadrangle,Idaho and Washington. Idaho Geological Survey Geologic Map 16.

Alexander, R.R. 1967. Site indexes for Engelmann spruce. U.S. Department ofAgriculture, Forest Service, Rocky Mountain Forest and Range ExperimentStation Research Paper, RP-32.

Alt, D.D., and D.W. Hyndman. 1989. Roadside geology of Idaho. Mountain PressPublishing, Missoula, Montana.

American Association of State Highway and Transportation Officials (AASHTO). 1998.Standard specifications for transportation materials and methods of samplingand testing. 19th edition, 2 volumes.

American Society for Testing and Materials (ASTM). 1998. Standard classification ofsoils for engineering purposes. ASTM Standard D 2487-00.

Bennett, E.H., R.S. Kopp, and J.H. Galbraith. 1975. Reconnaissance geology andgeochemistry of the Mt. Pend Oreille quadrangle and surrounding areas. IdahoGeological Survey Pamphlet 163.

Bond, J.G. 1978. Geologic map of Idaho. Idaho Geological Survey Geologic Map 1.

Bush, J.H. 1989. The Cambrian System of Northern Idaho and Northwestern Montana.In Chamberlain, V.E., R.M. Breckenridge, and B. Bonnichsen, editors.Guidebook to the geology of Northern and Western Idaho and surroundingarea. Idaho Geological Survey Bulletin 28.

Cochran, P.H. 1979a. Site index and height growth curves for managed, even-agedstands of Douglas-fir east of the Cascades in Oregon and Washington. U.S.Department of Agriculture, Forest Service, Pacific Northwest Forest and RangeExperiment Station Research Paper PNW-251.

Cochran, P.H. 1979b. Site index and height growth curves for managed, even-agedstands of white or grand fir east of the Cascades in Oregon and Washington.U.S. Department of Agriculture, Forest Service, Pacific Northwest Forest andRange Experiment Station Research Paper PNW-252.

Cochran, P.H. 1979c. Gross yields for even-aged stands of Douglas-fir and white orgrand fir east of the Cascades in Oregon and Washington. U.S. Department ofAgriculture, Forest Service, Pacific Northwest Forest and Range ExperimentStation Research Paper PNW-263.

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Cooper, S.V., K.E. Neiman, and D.W. Roberts. 1991. Forest habitat types of northernIdaho: a second approximation. U.S. Department of Agriculture, Forest Service,General Technical Report INT-236.

Haig, I.T. 1932. Second-growth yield, stand and volume tables for the western whitepine type. U.S. Department of Agriculture, Forest Service. Northern RockyMountain Forest Experiment Station Technical Bulletin 323.

Kirkham, V.R.D., and E.W. Ellis. 1926. Geology and ore deposits of Boundary County,Idaho. Idaho Geological Survey Bulletin 10.

Meyer, W.H. 1961. Yield of even-aged stands of ponderosa pine. U.S. Department ofAgriculture, Technical Bulletin 630. Washington, DC.

Portland Cement Association. 1973. PCA soil primer.

Ross, C.P., and J.D. Forrester. 1958. Outline of the geology of Idaho. Idaho GeologicalSurvey Bulletin 15.

Schmidt, W.C., R.C. Shearer, and A.L. Roe. 1976. Ecology and silviculture of westernlarch forests. U.S. Department of Agriculture, Forest Service Technical Bulletin1520.

Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service. U.S.Department of Agriculture Handbook 18.(http://soils.usda.gov/technical/manual/)

Soil Survey Staff. 1998. Keys to soil taxonomy. 8th edition. U.S. Department ofAgriculture, Natural Resources Conservation Service.(http://soils.usda.gov/technical/classification/tax_keys/)

Soil Survey Staff. 1999. Soil taxonomy: A basic system of soil classification for makingand interpreting soil surveys. 2nd edition. Natural Resources ConservationService. U.S. Department of Agriculture Handbook 436.(http://soils.usda.gov/technical/classification/taxonomy/)

United States Department of Agriculture, Natural Resources Conservation Service.National forestry handbook, title 190.(http://soils.usda.gov/technical/nfhandbook/)

United States Department of Agriculture, Natural Resources Conservation Service.National soil survey handbook, title 430-VI.(http://soils.usda.gov/technical/handbook/)

United States Department of Agriculture, Soil Conservation Service. 1961. Landcapability classification. U.S. Department of Agriculture Handbook 210.

United States Department of Agriculture, Soil Conservation Service. 1980. Soil surveyof Boundary County area, Idaho.

United States Department of Agriculture, Soil Conservation Service. 1984. Glossaryof selected geomorphic terms for western soil surveys.

United States Department of Agriculture, Soil Conservation Service. 1942. Preliminaryreport of water resources, Kootenai River Drainage, Boundary County, Idaho.

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Aeration, soil. The exchange of air in soil with airfrom the atmosphere. The air in a well-aeratedsoil is similar to that in the atmosphere; the air ina poorly aerated soil is considerably higher incarbon dioxide and lower in oxygen.

Aggregate, soil. Many fine particles held in a singlemass or cluster. Natural soil aggregates, such asgranules, blocks, or prisms, are called peds.Clods are aggregates produced by tillage orlogging.

Alluvial fan. A body of alluvium, with overflow ofwater and debris flow deposits, whose surfaceforms a segment of a cone that radiatesdownslope from the point where the streamemerges from a narrow valley onto a less slopingsurface. Source uplands range in relief and arealextent from mountains to gullied terrains onhillslopes.

Alluvium. Material, such as sand, silt, or clay,deposited on land by streams.

Alpha,alpha-dipyridyl. A dye that when dissolved in1N ammonium acetate is used to detect thepresence of reduced iron (Fe II) in the soil. Apositive reaction indicates a type of redox feature.

Animal-unit-month (AUM). The amount of foragerequired by one mature cow of approximately1,000 pounds weight, with or without a calf, for1 month.

Aquic conditions. Current soil wetnesscharacterized by saturation, reduction, and redoxfeatures.

Argillic horizon. A subsoil horizon characterized byan accumulation of illuvial clay.

Aspect. The direction in which a slope faces.Association, soil. A group of soils or miscellaneous

areas geographically associated in acharacteristic repeating pattern and defined anddelineated as a single map unit.

Available water capacity (available moisturecapacity). The capacity of soils to hold wateravailable for use by most plants. It is commonlydefined as the difference between the amount ofsoil water at field moisture capacity and theamount at wilting point. It is commonly expressedas inches of water per inch of soil. The capacity,

in inches, in a 60-inch profile or to a limiting layeris expressed as:

Very low ....................................................... 0 to 3.75

Low ........................................................... 3.75 to 5.0

Moderate .................................................... 5.0 to 7.5

High ..................................................... more than 7.5

Backslope. The geomorphic component that formsthe steepest inclined surface and principalelement of many hillslopes. Backslopes in profileare commonly steep and linear and descend to afootslope. In terms of gradational process,backslopes are erosional forms produced mainlyby mass wasting and running water.

Basal till. Compact glacial till deposited beneath theice.

Base saturation. The degree to which materialhaving cation-exchange properties is saturatedwith exchangeable bases (sum of Ca, Mg, Na,and K), expressed as a percentage of the totalcation-exchange capacity.

Bedrock. The solid rock that underlies the soil andother unconsolidated material or that is exposedat the surface.

Benchland. The nearly level to gently sloping land ona high terrace separated from a lower bottomlandby a steep escarpment.

Bottom land. The normal flood plain of a stream,subject to flooding.

Boulders. Rock fragments larger than 2 feet(60 centimeters) in diameter.

Bouldery. Refers to a soil with .01 to 0.1 percent ofthe surface covered with boulders.

Boundary, horizon. A zone or transitional layerbetween two adjoining horizons or layers, roughlyparallel to the soil surface. Boundaries vary indistinctness and topography.

Breakland. The steep and very steep broken land atthe border of an upland summit that is dissectedby ravines.

Calcareous soil. A soil containing enough calciumcarbonate (commonly combined with magnesiumcarbonate) to effervesce visibly when treated withcold, dilute hydrochloric acid.

Glossary

442 Soil Survey

Canopy. The leafy crown of trees or shrubs. (SeeCrown.)

Canyon. A long, deep, narrow, very steep sidedvalley with high, precipitous walls in an area ofhigh local relief.

Cation. An ion carrying a positive charge ofelectricity. The common soil cations are calcium,potassium, magnesium, sodium, and hydrogen.

Cation-exchange capacity. The total amount ofexchangeable cations that can be held by thesoil, expressed in terms of milliequivalents per100 grams of soil at neutrality (pH 7.0) or at someother stated pH value. The term, as applied tosoils, is synonymous with base-exchangecapacity but is more precise in meaning.

Chroma, soil color. (See Munsell notation.)Clay. As a soil separate, the mineral soil particles

less than 0.002 millimeters in diameter. As a soiltextural class, soil material that is 40 percent ormore clay, less than 45 percent sand, and lessthan 40 percent silt.

Clay film. A thin coating of oriented clay on thesurface of a soil aggregate or lining pores or rootchannels. Synonyms: clay coating, clay skin.

Claypan. A slowly permeable soil horizon thatcontains much more clay than the horizons aboveit. A claypan is commonly hard when dry andplastic or stiff when wet.

Closed depression. A low area completelysurrounded by higher ground and having nonatural outlet.

Coarse textured soil. Sand or loamy sand.Cobble (or cobblestone). A rounded or partly

rounded fragment of rock 3 to 10 inches (7.6 to25 centimeters) in diameter.

Cobbly soil material. Material that has 15 to35 percent, by volume, rounded or partiallyrounded rock fragments 3 to 10 inches (7.6 to25 centimeters) in diameter. Very cobbly soilmaterial has 35 to 60 percent of these rockfragments, and extremely cobbly soil materialhas more than 60 percent.

Codominant trees. Trees whose crowns form thegeneral level of the forest canopy and thatreceive full light from above but comparativelylittle from the sides.

COLE (coefficient of linear extensibility). (SeeLinear extensibility.)

Colluvium. Soil material or rock fragments, or both,moved by creep, slide, or local wash anddeposited at the base of steep slopes.

Complex, soil. A map unit of two or more kinds ofsoil or miscellaneous areas in such an intricatepattern or so small in area that it is not practical

to map them separately at the selected scale ofmapping. The pattern and proportion of the soilsor miscellaneous areas are somewhat similar inall areas.

Concretions. Grains, pellets, or nodules of varioussizes, shapes, and colors consisting ofconcentrated compounds or cemented soilgrains. The composition of most concretions isunlike that of the surrounding soil. Calciumcarbonate and iron oxide are commoncompounds in concretions.

Conglomerate. A coarse-grained, clastic rockcomposed of rounded or subangular rockfragments more than 2 millimeters in diameter. Itcommonly has a matrix of sand and finer-texturedmaterial. Conglomerate is the consolidatedequivalent of gravel.

Conservation tillage. Any tillage and plantingsystem in which a cover of crop residue ismaintained on at least 30 percent of the soilsurface after planting in order to reduce thehazard of water erosion. In areas where soilblowing is the primary concern, a system thatmaintains a cover of at least 1,000 pounds of flatresidue of small grain or the equivalent during thecritical erosion period.

Consistence, soil. Refers to the degree of cohesionand adhesion of soil material and its resistance todeformation when ruptured. Consistence includesresistance of soil material to rupture and topenetration; plasticity, toughness, and stickinessof puddled soil material; and the manner in whichthe soil material behaves when subject tocompression. Terms describing consistence aredefined in the “Soil Survey Manual” (Soil SurveyDivision Staff, 1993).

Consolidated sandstone. Sandstone that disperseswithin a few hours when fragments are placed inwater. The fragments are extremely hard or veryhard when dry, are not easily crushed, andcannot be textured by the usual field method.

Consolidated shale. Shale that disperses within afew hours when fragments are placed in water.The fragments are extremely hard or very hardwhen dry and are not easily crushed.

Control section. The part of the soil on whichclassification is based. The thickness variesamong different kinds of soil, but for many it isthat part of the soil profile between depths of10 inches and 40 or 80 inches.

Corrosion. Soil-induced electrochemical or chemicalaction that dissolves or weakens concrete oruncoated steel.

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Conservation cropping system. Growing crops incombination with needed cultural andmanagement practices. In a good conservationcropping system, the soil-improving crops andpractices more than offset the effects of the soil-depleting crops and practices. Cropping systemsare needed on all tilled soils. Soil-improvingpractices in a conservation cropping systeminclude the use of rotations that contain grassesand legumes and the return of crop residue to thesoil. Other practices include the use of greenmanure crops of grasses and legumes, propertillage, adequate fertilization, and weed and pestcontrol.

Cropping system. Growing crops according to aplanned system of rotation and managementpractices.

Cross-slope farming. Deliberately conductingfarming operations on sloping farmland in such away that tillage is across the general slope.

Crown. The upper part of a tree or shrub, includingthe living branches and their foliage.

Culmination of the mean annual increment CMAI).The average annual increase per acre in thevolume of a stand. Computed by dividing the totalvolume of the stand by its age. As the standincreases in age, the mean annual incrementcontinues to increase until mortality begins toreduce the rate of increase. The point where thestand reaches its maximum annual rate of growthis called the culmination of the mean annualincrement.

Cutbanks cave (in tables). The walls of excavationstend to cave in or slough.

Depth class. Depth to a restrictive or contrastinglayer defined as a range of depth. The nature ofthe restricting or contrasting layer is specified,unless it is consolidated bedrock which isunderstood. The following classes are used:

Very shallow ............................... less than 10 inches

Shallow ............................................. 10 to 20 inches

Moderately deep .............................. 20 to 40 inches

Deep ................................................. 40 to 60 inches

Very deep ................................. more than 60 inches

Depth, soil. Generally, the thickness of the soil overbedrock. Very deep soils are more than 60 inchesdeep over bedrock; deep soils, 40 to 60 inches;moderately deep, 20 to 40 inches; shallow, 10 to20 inches; and very shallow, less than 10 inches.

Diversion (or diversion terrace). A ridge of earth,generally a terrace, built to protect downslopeareas by diverting runoff from its natural course.

Dominant trees. Trees whose crowns form thegeneral level of the forest canopy and thatreceive full light from above and from the sides.

Drainage class (natural). Refers to the frequencyand duration of periods of saturation or partialsaturation during soil formation, as opposed toaltered drainage, which is commonly the result ofartificial drainage or irrigation but may be causedby the sudden deepening of channels or theblocking of drainage outlets. Seven classes ofnatural soil drainage are recognized:Excessively drained.—These soils have very highand high hydraulic conductivity and a low water-holding capacity. They are not suited to cropproduction unless irrigated.Somewhat excessively drained.—These soilshave high hydraulic conductivity and a low water-holding capacity. Without irrigation, only a narrowrange of crops can be grown, and yields are low.Well drained.—These soils have an intermediatewater-holding capacity. They retain optimumamounts of moisture, but they are not wet closeenough to the surface or long enough during thegrowing season to adversely affect yields.Moderately well drained.—These soils are wetclose enough to the surface or long enough thatplanting or harvesting operations or yields ofsome field crops are adversely affected unless adrainage system is installed. Moderately well-drained soils commonly have a layer with lowhydraulic conductivity, a wet layer relatively highin the profile, additions of water by seepage, orsome combination of these.Somewhat poorly drained.—These soils are wetclose enough to the surface or long enough thatplanting or harvesting operations or crop growthis markedly restricted unless a drainage systemis installed. Somewhat poorly drained soilscommonly have a layer with low hydraulicconductivity, a wet layer high in the profile,additions of water through seepage, or acombination of these.Poorly drained.—These soils commonly are sowet, at or near the surface, during a considerablepart of the year that field crops cannot be grownunder natural conditions. Poorly drainedconditions are caused by a saturated zone, alayer with low hydraulic conductivity, seepage, ora combination of these.Very poorly drained.—These soils are wet to thesurface most of the time. The wetness preventsthe growth of important crops (except rice) unlessa drainage system is installed.

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Drainage, surface. Runoff, or surface flow of water,from an area.

Drainageway. An area of ground at a lower elevationthan the surrounding ground and in which watercollects and is drained to a closed depressionor lake or to a drainageway at a lower elevation.A drainageway may or may not have distinctlyincised channels at its upper reaches orthroughout its course.

Droughty (in tables). The soil holds too little water(very low available water capacity) for plantsduring dry periods.

Duff. A generally firm organic layer on the surface ofmineral soils. It consists of fallen plant materialthat is in the process of decomposition andincludes everything from the litter on the surfaceto underlying pure humus.

Dune. A mound, ridge, or hill of loose, windblowngranular material (generally sand), either bare orcovered with vegetation.

Ecological site. An area where climate, soil, andrelief are sufficiently uniform to produce a distinctnatural plant community. An ecological site is theproduct of all the environmental factorsresponsible for its development. It is typified by anassociation of species that differ from those onother ecological sites in kind and/or proportion ofspecies or in total production.

Eluviation. The movement of material in true solutionor colloidal suspension from one place to anotherwithin the soil. Soil horizons that have lostmaterial through eluviation are eluvial; those thathave received material are illuvial.

Endosaturation. A type of saturation of the soil inwhich all horizons between the upper boundaryof saturation and a depth of 2 meters aresaturated.

Eolian soil material. Earthy parent materialaccumulated through wind action; commonlyrefers to sandy material in dunes or to loess inblankets on the surface.

Episaturation. A type of saturation indicating aperched water table in a soil in which saturatedlayers are underlain by one or more unsaturatedlayers within 2 meters of the surface.

Erosion. The wearing away of the land surface bywater, wind, ice, or other geologic agents and bysuch processes as gravitational creep.Erosion (geologic). Erosion caused by geologicprocesses acting over long geologic periods andresulting in the wearing away of mountains andthe building up of such landscape features asflood plains and coastal plains. Synonym: naturalerosion.

Erosion (accelerated). Erosion much more rapidthan geologic erosion, mainly as a result ofhuman or animal activities or of a catastrophe innature, such as fire, that exposes the surface.

Erosion hazard. An estimation of the severity ofsoil loss that could occur on a bare, disturbedsoil without benefit of cover for protection.Classes are slight, moderate, severe, and verysevere.

Escarpment. A relatively continuous and steep slopeor cliff breaking the general continuity of moregently sloping land surfaces and resulting fromerosion or faulting. Synonym: scarp.

Esker. A long, narrow, sinuous, steep-sided ridgecomposed of irregularly stratified sand and gravelthat were deposited by a subsurface streamflowing between ice walls or through ice tunnelsof a retreating glacier and that were left behindwhen the ice melted. Eskers range from less thana mile to more than 100 miles in length and from10 to 100 feet in height.

Even aged. Refers to a stand of trees in which onlysmall differences in age occur between individualtrees. A range of 20 years is allowed.

Fast intake (in tables). The rapid movement of waterinto the soil.

Fertility, soil. The quality that enables a soil toprovide plant nutrients, in adequate amounts andin proper balance, for the growth of specifiedplants when light, moisture, temperature, tilth,and other growth factors are favorable.

Fibric soil material (peat). The least decomposed ofall organic soil material. Peat contains a largeamount of well-preserved fiber that is readilyidentifiable according to botanical origin. Peat hasthe lowest bulk density and the highest watercontent at saturation of all organic soil material.

Field moisture capacity. The moisture content of asoil, expressed as a percentage of the ovendryweight, after the gravitational, or free, water hasdrained away; the field moisture content 2 or 3days after a soaking rain; also called normal fieldcapacity, normal moisture capacity, or capillarycapacity.

Fill slope. A sloping surface consisting of excavatedsoil material from a road cut. It commonly is onthe downhill side of the road.

Fine textured soil. Sandy clay, silty clay, or clay.Flood plain. A nearly level alluvial plain that borders

a stream and is subject to flooding unlessprotected artificially.

Fluvial. Of or pertaining to rivers; produced by riveraction, as a fluvial plain.

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Foothill. A steeply sloping upland that has relief of asmuch as 1,000 feet (300 meters) and fringes amountain range or high-plateau escarpment.

Footslope. The geomorphic component that formsthe inner, gently inclined surface at the base of ahillslope. The surface profile is dominantlyconcave. In terms of gradational processes, afootslope is a transitional zone between anupslope site of erosion (backslope) and adownslope site of deposition (toeslope).

Forb. Any herbaceous plant not a grass or a sedge.Forest cover. All trees and other woody plants

(underbrush) covering the ground in a forest.Forest habitat type. A stand of trees similar in

composition and development because of givenphysical and biological factors by which it may bedifferentiated from other stands.

Frost action (in tables). Freezing and thawing of soilmoisture. Frost action can damage roads,buildings and other structures, and plant roots.

Genesis, soil. The mode of origin of the soil. Refersespecially to the processes or soil-forming factorsresponsible for the formation of the solum, or truesoil, from the unconsolidated parent material.

Glacial drift. Pulverized and other rock materialtransported by glacial ice and then deposited.Also, the sorted and unsorted material depositedby streams flowing from glaciers.

Glacial outwash. Gravel, sand, and silt, commonlystratified, deposited by glacial meltwater.

Glacial till. Unsorted, nonstratified glacial driftconsisting of clay, silt, sand, and boulderstransported and deposited by glacial ice.

Glacial trough. A broad, elongate U-shaped valleydeveloped by glacial movement.

Glaciofluvial deposits. Material moved by glaciersand subsequently sorted and deposited bystreams flowing from the melting ice. Thedeposits are stratified and occur as kames,eskers, deltas, and outwash plains.

Glaciolacustrine deposits. Material ranging fromfine clay to sand derived from glaciers anddeposited in glacial lakes mainly by glacialmeltwater. Many deposits are interbedded orlaminated.

Gleyed soil. Soil that formed under poor drainage,resulting in the reduction of iron and otherelements in the profile and in gray colors.

Grassed waterway. A natural or constructedwaterway, typically broad and shallow, seeded tograss as protection against erosion. Conductssurface water away from cropland.

Gravel. Rounded or angular fragments of rockas much as 3 inches (2 millimeters to

7.6 centimeters) in diameter. An individual pieceis a pebble.

Gravelly soil material. Soil that is 15 to 35 percent,by volume, rounded or angular rock fragments upto 3 inches (7.6 centimeters) in diameter. Verygravelly soil is 35 to 60 percent gravel, andextremely gravelly soil is more than 60 percentgravel by volume.

Green manure crop (agronomy). A soil-improvingcrop grown to be plowed under in an early stageof maturity or soon after maturity.

Ground water. Water filling all the unblocked pores ofthe material below the water table.

Gully. A miniature valley with steep sides cut byrunning water and through which water ordinarilyruns only after rainfall. The distinction between agully and a rill is one of depth. A gully generally isan obstacle to farm machinery and is too deep tobe obliterated by ordinary tillage; a rill is of lesserdepth and can be smoothed over by ordinarytillage.

Gypsum. A mineral consisting of hydrous calciumsulfate.

Habitat type. An aggregation of all land areascapable of producing similar climax plantcommunities.

Hard bedrock. Bedrock that cannot be excavatedexcept by blasting or by the use of specialequipment that is not commonly used inconstruction.

Hardpan. A hardened or cemented soil horizon, orlayer. The soil material is sandy, loamy, or clayeyand is cemented by iron oxide, silica, calciumcarbonate, or other substance.

Heavy metal. Inorganic substances that are solid atordinary temperatures and are not soluble inwater. They form oxides and hydroxides that arebasic. Examples are copper, iron, cadmium, zinc,manganese, lead, and arsenic.

Hemic soil material (mucky peat). Organic soilmaterial intermediate in degree of decompositionbetween the less decomposed fibric material andthe more decomposed sapric material.

Hill. A natural elevation of the land surface, rising asmuch as 1,000 feet above surrounding lowlands,commonly of limited summit area and having awell-defined outline; hillsides generally haveslopes of more than 8 percent. The distinctionbetween a hill and a mountain is arbitrary and isdependent on local usage.

Horizon, soil. A layer of soil, approximately parallel tothe surface, having distinct characteristicsproduced by soil-forming processes. In theidentification of soil horizons, an uppercase letter

446 Soil Survey

represents the major horizons. Numbers orlowercase letters that follow representsubdivisions of the major horizons. Anexplanation of the subdivisions is given in the“Soil Survey Manual” (Soil Survey Division Staff,1993). The major horizons of mineral soil are asfollows:O horizon.—An organic layer of fresh anddecaying plant residue.A horizon.—The mineral horizon at or near thesurface in which an accumulation of humifiedorganic matter is mixed with the mineral material.Also, a plowed surface horizon, most of whichwas originally part of a B horizon.E horizon.—The mineral horizon in which themain feature is loss of silicate clay, iron,aluminum, or some combination of these.B horizon.—The mineral horizon below an A orE horizon. The B horizon is in part a layer oftransition from the overlying A to the underlyingC horizon. The B horizon also has distinctivecharacteristics, such as (1) accumulation of clay,sesquioxides, humus, or a combination of these;(2) prismatic or blocky structure; (3) redder orbrowner colors than those in the A horizon; or(4) a combination of these.C horizon.—The mineral horizon or layer,excluding indurated bedrock, that is little affectedby soil-forming processes and does not have theproperties typical of the overlying soil material.The material of a C horizon may be either like orunlike that in which the solum formed. If thematerial is known to differ from that in the solum,an Arabic numeral, commonly a 2, precedes theletter C.Cr horizon.—Sedimentary beds of consolidatedsandstone and semiconsolidated andconsolidated shale. Generally, roots canpenetrate this horizon only along fracture planes.R layer.—Consolidated bedrock beneath the soil.The bedrock commonly underlies a C horizon,but it can be directly below an A or a B horizon.

Hue, soil color. (See Munsell notation.)Humus. The well-decomposed, more or less stable

part of the organic matter in mineral soils.Hydrologic soil groups. Refers to soils grouped

according to their runoff-producingcharacteristics. The chief consideration is theinherent capacity of soil bare of vegetation topermit infiltration. The slope and the kind of plantcover are not considered but are separate factorsin predicting runoff. Soils are assigned to fourgroups. In group A are soils having a highinfiltration rate when thoroughly wet and having a

low runoff potential. They are mainly deep, welldrained, and sandy or gravelly. In group D, at theother extreme, are soils having a very slowinfiltration rate and thus a high runoff potential.They have a claypan or clay layer at or near thesurface, have a permanent high water table, orare shallow over nearly impervious bedrock orother material. A soil is assigned to twohydrologic groups if part of the acreage isartificially drained and part is undrained.

Igneous rock. Rock formed by solidification from amolten or partially molten state. Major varietiesinclude plutonic and volcanic rock. Examples areandesite, basalt, and granite.

Illuviation. The movement of soil material from onehorizon to another in the soil profile. Generally,material is removed from an upper horizon anddeposited in a lower horizon.

Impervious soil. A soil through which water, air, orroots penetrate slowly or not at all. No soil isabsolutely impervious to air and water all thetime.

Infiltration. The downward entry of water into theimmediate surface of soil or other material, ascontrasted with percolation, which is movementof water through soil layers or material.

Infiltration rate. The rate at which water penetratesthe surface of the soil at any given instant,usually expressed in inches per hour. The ratecan be limited by the infiltration capacity of thesoil or the rate at which water is applied at thesurface.

Intake rate. The average rate of water entering thesoil under irrigation. Most soils have a fast initialrate; the rate decreases with application time.Therefore, intake rate for design purposes is nota constant but is a variable depending on the netirrigation application. The rate of water intake, ininches per hour, is expressed as follows:

Less than 0.2 ............................................... very low

0.2 to 0.4 .............................................................. low

0.4 to 0.75 ......................................... moderately low

0.75 to 1.25 ................................................ moderate

1.25 to 1.75 ..................................... moderately high

1.75 to 2.5 .......................................................... high

More than 2.5 ............................................. very high

Irrigation. Application of water to soils to assist inproduction of crops. Methods of irrigation are:Basin.—Water is applied rapidly to nearly levelplains surrounded by levees or dikes.Border.—Water is applied at the upper end of astrip in which the lateral flow of water is controlled

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by small earth ridges called border dikes, orborders.Controlled flooding.—Water is released atintervals from closely spaced field ditches anddistributed uniformly over the field.Corrugation.—Water is applied to small, closelyspaced furrows or ditches in fields of close-growing crops or in orchards so that it flows inonly one direction.Drip (or trickle).—Water is applied slowly andunder low pressure to the surface of the soil orinto the soil through such applicators as emitters,porous tubing, or perforated pipe.Furrow.—Water is applied in small ditches madeby cultivation implements. Furrows are used fortree and row crops.Sprinkler.—Water is sprayed over the soil surfacethrough pipes or nozzles from a pressure system.Subirrigation.—Water is applied in open ditchesor tile lines until the water table is raised enoughto wet the soil.Wild flooding.—Water, released at high points, isallowed to flow onto an area without controlleddistribution.

Ksat. Saturated hydraulic conductivity. (SeePermeability.)

Kame. A moundlike hill of glacial drift, composedchiefly of stratified sand and gravel.

Landslide. The rapid downhill movement of a massof soil and loose rock, generally when wet orsaturated. The speed and distance of movement,as well as the amount of soil and rock material,vary greatly.

Large stones (in tables). Rock fragments 3 inches(7.6 centimeters) or more across. Large stonesadversely affect the specified use of the soil.

Lateral moraine. A ridgelike moraine carried on anddeposited at the side margin of a valley glacier. Itis composed chiefly of rock fragments derivedfrom the valley walls by glacial abrasion andplucking or by mass wasting.

Leaching. The removal of soluble material from soilor other material by percolating water.

Linear extensibility. Refers to the change in lengthof an unconfined clod as moisture content isdecreased from a moist to a dry state. Linearextensibility is used to determine the shrink-swellpotential of soils. It is an expression of the volumechange between the water content of the clod at1/3- or 1/10-bar tension (33kPa or 10kPa tension)and oven dryness. Volume change is influencedby the amount and type of clay minerals in thesoil. The volume change is the percent change forthe whole soil. If it is expressed as a fraction, the

resulting value is COLE, coefficient of linearextensibility.

Liquid limit. The moisture content at which the soilpasses from a plastic to a liquid state.

Loam. Soil material that is 7 to 27 percent clayparticles, 28 to 50 percent silt particles, and lessthan 52 percent sand particles.

Loess. Fine-grained material, dominantly of silt-sizedparticles, deposited by wind.

Low strength. The soil is not strong enough tosupport loads.

Masses. Concentrations of substances in the soilmatrix that do not have a clearly definedboundary with the surrounding soil material andcannot be removed as a discrete unit. Commoncompounds making up masses are calciumcarbonate, gypsum or other soluble salts, ironoxide, and manganese oxide. Masses consistingof iron oxide or manganese oxide generally areconsidered a type of redox concentration.

Mean annual increment (MAI). The average annualincrease in volume of a tree during its entire life.

Medium textured soil. Very fine sandy loam, loam,silt loam, or silt.

Metamorphic rock. Rock of any origin altered inmineralogical composition, chemical composition,or structure by heat, pressure, and movement.Nearly all such rocks are crystalline.

Metasedimentary rock. Sedimentary rock of anyorigin that is partially altered in mineralogicalcomposition, chemical composition, or structureby heat, pressure, and movement. Examples arethe Belt series of rocks which include siltite,argillite, and quartzite.

Mineral soil. Soil that is mainly mineral material andlow in organic material. Its bulk density is morethan that of organic soil.

Minimum tillage. Only the tillage essential to cropproduction and prevention of soil damage.

Miscellaneous area. An area that has little or nonatural soil and supports little or no vegetation.

Moderately coarse textured soil. Coarse sandyloam, sandy loam, or fine sandy loam.

Moderately fine textured soil. Clay loam, sandy clayloam, or silty clay loam.

Mollic epipedon. A thick, dark, humus-rich surfacehorizon (or horizons) that has high basesaturation and pedogenic soil structure. It mayinclude the upper part of the subsoil.

Moraine. An accumulation of glacial drift in atopographic landform of its own, resulting chieflyfrom the direct action of glacial ice. Some typesare lateral, recessional, and terminal.

448 Soil Survey

Morphology, soil. The physical makeup of the soil,including the texture, structure, porosity,consistence, color, and other physical, mineral,and biological properties of the various horizons,and the thickness and arrangement of thosehorizons in the soil profile.

Mottling, soil. Areas of color that differ from thematrix color. These colors are commonlyattributes retained from the geologic parentmaterial. (See Redox features for indications ofpoor aeration and impeded drainage.)

Mountain. A natural elevation of the land surface,rising more than 1,000 feet above surroundinglowlands, commonly of restricted summit area(relative to a plateau) and generally having steepsides. A mountain can occur as a single, isolatedmass or in a group forming a chain or range.

Muck. Dark, finely divided, well-decomposed organicsoil material. (See Sapric soil material.)

Mudstone. Sedimentary rock formed by induration ofsilt and clay in approximately equal amounts.

Munsell notation. A designation of color by degreesof three simple variables—hue, value, andchroma. For example, a notation of 10YR 6/4 isa color with hue of 10YR, value of 6, and chromaof 4.

Nutrient, plant. Any element taken in by a plantessential to its growth. Plant nutrients are mainlynitrogen, phosphorus, potassium, calcium,magnesium, sulfur, iron, manganese, copper,boron, and zinc obtained from the soil andcarbon, hydrogen, and oxygen obtained from theair and water.

Organic matter. Plant and animal residue in the soilin various stages of decomposition. The contentof organic matter in the surface layer is describedas follows:

Very low ................................... less than 0.5 percent

Low ................................................ 0.5 to 1.0 percent

Moderately low .............................. 1.0 to 2.0 percent

Moderate ....................................... 2.0 to 4.0 percent

High ............................................... 4.0 to 8.0 percent

Very high ............................... more than 8.0 percent

Outwash plain. An extensive area of glaciofluvialmaterial that was deposited by meltwaterstreams.

Pan. A compact, dense layer in a soil that impedesthe movement of water and the growth of roots.For example, hardpan, fragipan, claypan,plowpan, and traffic pan.

Parent material. The unconsolidated organic andmineral material in which soil forms.

Peat. Unconsolidated material, largelyundecomposed organic matter, that hasaccumulated under excess moisture. (See Fibricsoil material.)

Ped. An individual natural soil aggregate, such as agranule, a prism, or a block.

Pedon. The smallest volume that can be called“a soil.” A pedon is three dimensional and largeenough to permit study of all horizons. Itsarea ranges from about 10 to 100 square feet(1 square meter to 10 square meters), dependingon the variability of the soil.

Percolation. The movement of water through the soil.Percs slowly (in tables). The slow movement of water

through the soil, adversely affecting the specifieduse.

Permeability. The quality of the soil that enableswater or air to move downward through theprofile.

Terms describing permeability are:

Very slow ..................................... less than 0.06 inch

Slow .................................................. 0.06 to 0.2 inch

Moderately slow ................................. 0.2 to 0.6 inch

Moderate ........................................ 0.6 to 2.0 inches

Moderately rapid ............................ 2.0 to 6.0 inches

Rapid ............................................... 6.0 to 20 inches

Very rapid ................................. more than 20 inches

pH value. A numerical designation of acidity andalkalinity in soil. (See Reaction, soil.)

Phase, soil. A subdivision of a soil series based onfeatures that affect its use and management,such as slope, stoniness, and flooding.

Piping (in tables). Formation of subsurface tunnels orpipelike cavities by water moving through the soil.

Plastic limit. The moisture content at which a soilchanges from semisolid to plastic.

Plasticity index. The numerical difference betweenthe liquid limit and the plastic limit. The range ofmoisture content within which the soil remainsplastic.

Ponding. Standing water on soils in closeddepressions. Unless the soils are artificiallydrained, the water can be removed only bypercolation or evapotranspiration.

Potential natural community (PNC). The bioticcommunity that would become established on anecological site if all successional sequences werecompleted without interferences by man underthe present environmental conditions. Naturaldisturbances are inherent in its development. ThePNC may include acclimatized or naturalizednonnative species.

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Potential rooting depth (effective rooting depth).Depth to which roots could penetrate if thecontent of moisture in the soil were adequate.The soil has no properties restricting thepenetration of roots to this depth.

Productivity, soil. The capability of a soil forproducing a specified plant or sequence of plantsunder specific management.

Profile, soil. A vertical section of the soil extendingthrough all its horizons and into the parentmaterial.

Quartzite, metamorphic. Rock consisting mainly ofquartz that formed through recrystallization ofquartz-rich sandstone or chert.

Quartzite, sedimentary. Very hard butunmetamorphosed sandstone consisting chieflyof quartz grains.

Reaction, soil. A measure of acidity or alkalinity of asoil, expressed in pH values. A soil that tests topH 7.0 is described as precisely neutral inreaction because it is neither acid nor alkaline.The degrees of acidity or alkalinity, expressed aspH values, are:

Ultra acid .............................................. less than 3.5

Extremely acid ........................................... 3.5 to 4.4

Very strongly acid ...................................... 4.5 to 5.0

Strongly acid .............................................. 5.1 to 5.5

Moderately acid .......................................... 5.6 to 6.0

Slightly acid ................................................ 6.1 to 6.5

Neutral ........................................................ 6.6 to 7.3

Slightly alkaline .......................................... 7.4 to 7.8

Moderately alkaline .................................... 7.9 to 8.4

Strongly alkaline ........................................ 8.5 to 9.0

Very strongly alkaline ......................... 9.1 and higher

Redox concentrations. Nodules, concretions, softmasses, pore linings, and other features resultingfrom the accumulation of iron or manganeseoxide. An indication of chemical reduction andoxidation resulting from saturation.

Redox depletions. Low-chroma zones from whichiron and manganese oxide or a combination ofiron and manganese oxide and clay has beenremoved. These zones are indications of thechemical reduction of iron resulting fromsaturation.

Redox features. Redox concentrations, redoxdepletions, reduced matrices, a positive reactionto alpha,alpha-dipyridyl, and other featuresindicating the chemical reduction and oxidation ofiron and manganese compounds resulting fromsaturation.

Regeneration. The new growth of a natural plantcommunity, developing from seed.

Relief. The elevations or inequalities of a landsurface, considered collectively.

Residuum (residual soil material). Unconsolidated,weathered or partly weathered mineral materialthat accumulated as consolidated rockdisintegrated in place.

Rill. A steep-sided channel resulting from acceleratederosion. A rill generally is a few inches deep andnot wide enough to be an obstacle to farmmachinery.

Riverwash. Unstable areas of sandy, silty, clayey, orgravelly sediments. These areas are flooded,washed, and reworked by rivers so frequentlythat they support little or no vegetation.

Road cut. A sloping surface produced by mechanicalmeans during road construction. It is commonlyon the uphill side of the road.

Rock fragments. Rock or mineral fragments havinga diameter of 2 millimeters or more; for example,boulders, stones, cobbles, and gravel.

Rock outcrop. Exposures of bare bedrock other thanlava flows and rock-lined pits.

Root zone. The part of the soil that can bepenetrated by plant roots.

Rooting depth (in tables). Shallow root zone. Thesoil is shallow over a layer that greatly restrictsroots.

Runoff. The precipitation discharged into streamchannels from an area. The water that flows offthe surface of the land without sinking into thesoil is called surface runoff. Water that enters thesoil before reaching surface streams is calledground-water runoff or seepage flow from groundwater.

Salinity. The electrical conductivity of a saline soil. Itis expressed, in millimhos per centimeter, asfollows:

Nonsaline ......................................................... 0 to 4

Slightly saline ................................................... 4 to 8

Moderately saline ........................................... 8 to 16

Strongly saline ..................................... more than 16

Sand. As a soil separate, individual rock or mineralfragments from 0.05 to 2.0 millimeters indiameter. Most sand grains consist of quartz. Asa soil textural class, a soil that is 85 percent ormore sand and not more than 10 percent clay.

Sandstone. Sedimentary rock containing dominantlysand-sized particles.

Sandy soil. Sand or loamy sand.Sapric soil material (muck). The most highly

decomposed of all organic soil material. Muckhas the least amount of plant fiber, the highest

450 Soil Survey

bulk density, and the lowest water content atsaturation of all organic soil material.

Saturation. Wetness characterized by zero orpositive pressure of the soil water. Underconditions of saturation, the water will flow fromthe soil matrix into an unlined auger hole.

Sedimentary rock. Rock made up of particlesdeposited from suspension in water. The chiefkinds of sedimentary rock are conglomerate,formed from gravel; sandstone, formed fromsand; shale, formed from clay; and limestone,formed from soft masses of calcium carbonate.There are many intermediate types. Some wind-deposited sand is consolidated into sandstone.

Seepage (in tables). The movement of water throughsoil. Seepage adversely affects the specified use.

Series, soil. A group of soils that have profiles thatare almost alike, except for differences in textureof the surface layer or of the underlying material.All the soils of a series have horizons that aresimilar in composition, thickness, andarrangement.

Shale. Sedimentary rock formed by the hardening ofa clay deposit.

Shrink-swell (in tables). The shrinking of soil whendry and the swelling when wet. Shrinking andswelling can damage roads, dams, buildingfoundations, and other structures. It can alsodamage plant roots.

Side slope. A geomorphic component of hillsconsisting of a laterally planar area of a hillside.The overland waterflow is predominantly parallel.

Silica. A combination of silicon and oxygen. Themineral form is called quartz.

Silt. As a soil separate, individual mineral particlesthat range in diameter from the upper limit of clay(0.002 millimeters) to the lower limit of very finesand (0.05 millimeters). As a soil textural class,soil that is 80 percent or more silt and less than12 percent clay.

Siltstone. Sedimentary rock made up of dominantlysilt-sized particles.

Similar soils. Soils that share limits of diagnosticcriteria, behave and perform in a similar manner,and have similar conservation needs ormanagement requirements for the major landuses in the survey area.

Site index. A designation of the quality of a forest sitebased on the height of the dominant stand at anarbitrarily chosen age. For example, if theaverage height attained by dominant or dominantand codominant trees in a fully stocked stand atthe age of 50 years is 75 feet, the site index is 75.

Slippage. Soil mass susceptible to movementdownslope when loaded, excavated, or wet. (SeeSlumping.)

Slope. The inclination of the land surface from thehorizontal. Percentage of slope is the verticaldistance divided by horizontal distance, thenmultiplied by 100. Thus, a slope of 20 percent is adrop of 20 feet in 100 feet of horizontal distance.In this survey the following slope classes arerecognized:

Nearly level ......................................... 0 to 2 percent

Gently sloping ..................................... 2 to 4 percent

Moderately sloping .............................. 4 to 8 percent

Strongly sloping ................................ 8 to 15 percent

Moderately steep ............................ 15 to 25 percent

Steep ............................................... 25 to 45 percent

Very steep .............................. more than 45 percent

Slope (in tables). Slope is great enough that specialpractices are required to ensure satisfactoryperformance of the soil for a specific use.

Slow refill (in tables). The slow filling of ponds,resulting from restricted permeability in the soil.

Slumping. The soil mass is susceptible to movementdownslope, usually with a backward rotation,when loaded, excavated, or wet. (See Slippage)

Sodium adsorption ratio (SAR). A measure of theamount of sodium (Na) relative to calcium (Ca)and magnesium (Mg) in the water extract fromsaturated soil paste. It is the ratio of the Naconcentration divided by the square root of one-half of the Ca + Mg concentration.

Soft bedrock. Bedrock that can be excavated withtrenching machines, backhoes, small rippers, andother equipment commonly used in construction.

Soil. A natural, three-dimensional body at the earth’ssurface. It is capable of supporting plants and hasproperties resulting from the integrated effect ofclimate and living matter acting on earthy parentmaterial, as conditioned by relief over time.

Solum. The upper part of a soil profile, above theC horizon, in which the processes of soilformation are active. The solum in soil consistsof the A, E, and B horizons. Generally, thecharacteristics of the material in these horizonsare unlike those of the material below the solum.The living roots and plant and animal activitiesare largely confined to the solum.

Species. A single, distinct kind of plant or animalhaving certain distinguishing characteristics.

Stones. Rock fragments 10 to 24 inches (25 to60 centimeters) in diameter if rounded or 15 to24 inches (38 to 60 centimeters) in length if flat.

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Stony. Refers to a soil containing stones in numbersthat interfere with tillage, or stones cover .01 to0.1 percent of the surface. Very stony meansthat 0.1 to 3.0 percent of the surface is coveredwith stones. Extremely stony means that 3 to15 percent of the surface is covered with stones.

Stream channel. The hollow bed where a naturalstream of surface water flows or may flow; thedeepest or central part of the bed, formed by themain current and covered more or lesscontinuously by water.

Stream terrace. One of a series of platforms in astream valley, flanking and more or less parallelto the stream channel. It originally formed nearthe level of the stream and is the dissectedremnants of an abandoned flood plain,streambed, or valley floor that were producedduring a former stage of erosion or deposition.

Stripcropping. Growing crops in a systematicarrangement of strips or bands that providevegetative barriers to soil blowing and watererosion.

Structure, soil. The arrangement of primary soilparticles into compound particles or aggregates.The principal forms of soil structure are platy(laminated), prismatic (vertical axis of aggregateslonger than horizontal), columnar (prisms withrounded tops), blocky (angular or subangular),and granular. Structureless soils are either singlegrain (each grain by itself, as in dune sand) ormassive (the particles adhering without anyregular cleavage, as in many hardpans).

Subsoil. Technically, the B horizon; roughly, the partof the solum below plow depth.

Substratum. The part of the soil below the solum.Subsurface layer. Any surface soil horizon (A, E, AB,

or EB) below the surface layer.Summit. A general term for the top, or highest level,

of an upland feature, such as a hill or mountain. Itcommonly refers to a higher area that has agentle slope and is flanked by steeper slopes.

Surface layer. The soil ordinarily moved in tillage, orits equivalent in uncultivated soil, ranging indepth from 4 to 10 inches (10 to 25 centimeters).Frequently designated as the “plow layer,” or the“Ap horizon.”

Terrace. An embankment, or ridge, constructedacross sloping soils on the contour or at a slightangle to the contour. The terrace interceptssurface runoff so that water soaks into the soil orflows slowly to a prepared outlet. A terrace in afield generally is built so that the field can befarmed. A terrace intended mainly for drainage

has a deep channel that is maintained inpermanent sod.

Terrace (geologic). An old alluvial plain, ordinarilyflat or undulating, bordering a river, a lake, or thesea.

Texture, soil. The relative proportions of sand, silt,and clay particles in a mass of soil. The basictextural classes, in order of increasing proportionof fine particles, are sand, loamy sand, sandyloam, loam, silt loam, silt, sandy clay loam, clayloam, silty clay loam, sandy clay, silty clay, andclay. The sand, loamy sand, and sandy loamclasses may be further divided by specifying“coarse,” “fine,” or “very fine.”

Thin layer (in tables). A layer of otherwise suitablesoil material that is too thin for the specified use.

Tilth, soil. The physical condition of the soil asrelated to tillage, seedbed preparation, seedlingemergence, and root penetration.

Toeslope. The outermost inclined surface at the baseof a hill. Toeslopes are commonly gentle andlinear in profile.

Topsoil. The upper part of the soil, which is the mostfavorable material for plant growth. It is ordinarilyrich in organic matter and is used to topdressroadbanks, lawns, and land affected by mining.

Trace elements. Chemical elements, for example,zinc, cobalt, manganese, copper, and iron, insoils in extremely small amounts. They areessential to plant growth.

Trafficability. The degree to which a soil is capableof supporting vehicular traffic across a widerange in soil moisture conditions.

Understory. Any plants in a forest community thatgrow to a height of less than 5 feet.

Upland. Land at a higher elevation, in general, thanthe alluvial plain or stream terrace; land abovethe lowlands along streams.

Valley. An elongated depressional area primarilydeveloped by stream action.

Valley fill. In glaciated regions, material deposited instream valleys by glacial meltwater. Innonglaciated regions, alluvium deposited byheavily loaded streams.

Value, soil color. (See Munsell notation.)Variegation. Refers to patterns of contrasting colors

assumed to be inherited from the parent materialrather than to be the result of poor drainage.

Volcanic ash mantle. A surface layer of soil thatcontains 30 percent or more volcanic glass,covering older soil material. It has low bulkdensity and high water holding capacity.

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Water table. A saturated zone of free water in thesoil.

Weathering. All physical and chemical changesproduced in rocks or other deposits at or near theearth’s surface by atmospheric agents. Thesechanges result in disintegration anddecomposition of the material.

Wetness (in tables). The soil is wet from saturationby a high water table during the period of use.

Wilting point (or permanent wilting point). Themoisture content of soil, on an ovendry basis, atwhich a plant (specifically a sunflower) wilts somuch that it does not recover when placed in ahumid, dark chamber.

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