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46
<br />Permeability of this Camas soil is very rapid. Available
<br />water capacity is about 1.5 to 3.5 inches. Water
<br />supplying capacity is 10 to 18 inches. Effective rooting
<br />depth is 8 to 14 inches. It is limited by the very gravelly
<br />substratum. Runoff is slow, and the hazard of water
<br />erosion is slight except during periods of overflow from
<br />flooding of nearby streams. The soil is subject to only
<br />rare periods of flooding because of the construction of
<br />large dams on the major rivers.
<br />The disturbed Camas soil has been covered by as
<br />much as 40 inches of fill material or has had as much as
<br />30 inches of the original profile removed by cutting or
<br />grading. The fill material is commonly from adjacent
<br />areas of Camas, Newberg, or Cloquato soils that have
<br />been cut or graded. The disturbed areas have highly
<br />variable properties.
<br />Urban land consists of areas where the soils are
<br />largely covered by concrete, asphalt, buildings, or other
<br />impervious surfaces that obscure or alter the soils so
<br />that identification is not feasible.
<br />This unit is used mainly for urban development. It is
<br />also used for yards and as open areas around and
<br />between buildings.
<br />If this unit is used for urban development, the main
<br />limitation is the hazard of rare flooding from prolonged,
<br />heavy rainfall and snowmelt that fill the large reservoirs
<br />upstream and override the effect of the dams. The
<br />chance of such an event occurring is about once in 100
<br />years, although the chance of a storm occurring that
<br />might cause minor damage and isolation of some areas
<br />by water flowing through some of the lower channels in
<br />the unit is once in 50 years.
<br />In.summer, irrigation is required for lawn grasses,
<br />shrubs, vines, shade trees, and ornamental trees. Plants
<br />that tolerate droughtiness should be selected if irrigation
<br />is not provided.
<br />This. map unit is not assigned a capability
<br />classification.
<br />24-Chapman loam. This deep, well drained soil is on
<br />low river terraces. It formed in recent mixed alluvium.
<br />Slopes are 0 to 3 percent. Areas are elongated in shape
<br />and are 3 to 100 acres or more in size. The vegetation in
<br />areas not cultivated is mainly Douglas-fir, bigleaf maple,
<br />Oregon white oak, blackbery, shrubs, and grasses.
<br />Elevation is 300 to 1,000 feet. The average annual
<br />precipitation is 40 to 60 inches, the average annua! air
<br />temperature is 52 to 54 degrees F, and the average
<br />frost-free period is 165 to 210 days.
<br />Typically, the upper part of the surface layer is dark
<br />brown loam about 8 inches thick and the lower part is
<br />very dark grayish brown clay loam about 6 inches thick.
<br />The subsoil is dark brown and dark yellowish brown
<br />loam about 28 inches thick. The upper part of the
<br />substratum is brown gravelly sandy loam about 8 inches
<br />thick, and the lower part to a depth of 60 inches or more
<br />is dark brown very gravelly sandy loam.
<br />Soil Survey
<br />Included in this unit are small areas of Chehalis,
<br />Malabon, McBee, and Salem soils. Included areas make
<br />up about 15 percent of the total acreage.
<br />Permeability of this Chapman soil is moderate.
<br />Available water capacity is about 8 to 12 inches. Water
<br />supplying capacity is 19 to 24 inches. Effective rooting
<br />depth is 60 inches or more. Runoff is slow, and the
<br />hazard of water erosion is slight. This soil is subject to
<br />rare periods of flooding.
<br />This unit is used mainly for row crops, grass seed, and
<br />small grain. It is also used for orchards, recreation,
<br />pasture, homesites, and urban development.
<br />This unit is suited to all climatically adapted crops. It is
<br />most valued for root crops such as carrots because the
<br />surface layer can be easily dug.
<br />In summer, irrigation is required for maximum
<br />production of most crops. Sprinkler irrigation is a suitable
<br />method of applying water. Use of this method permits
<br />the even, controlled application of water, reduces runoff,
<br />and minimizes the risk of erosion.
<br />Returning all crop residue to the soil and using a
<br />cropping system that includes grasses, legumes, or
<br />grass-legume mixtures help to maintain fertility and tilth.
<br />Grain and grasses respond to nitrogen; legumes respond
<br />to phosphorus, boron, sulfur, and lime; and vegetables
<br />and berries respond to nitrogen, phosphorus, and
<br />potassium.
<br />This unit is suited to pasture. Proper stocking rates,
<br />pasture rotation, and restricted grazing during wet
<br />periods help to keep the pasture in good condition and
<br />to protect the soil from erosion.
<br />If this unit is used for homesite development, the main
<br />limitation is the hazard of flooding. Flooding can be
<br />controlled only by use of major flood. control structures.
<br />Dikes and channels that have outlets to bypass
<br />floodwater can be used to protect buildings and onsite
<br />sewage disposal systems from flooding.
<br />In summer, irrigation is required for lawn grasses,
<br />shrubs, vines, shade trees, and ornamental trees. Plants
<br />that tolerate droughtiness should be selected if irrigation
<br />is not provided.
<br />This unit is in capability class I.
<br />25=Chapman-Urban land complex. This map unit is
<br />on low river terraces. Slope is 0 to 3 percent. Areas are
<br />elongated in shape and are 3 to 100 acres in size. The
<br />native vegetation is mainly Douglas-fir, bigleaf maple,
<br />Oregon white oak, blackberry, shrubs, and grasses.
<br />Elevation is 300 to 1,000 feet. The average annual
<br />precipitation is 40 to 60 inches, the average annual air.
<br />temperature is 52 to 54 degrees F, and the average
<br />frost-free period is 165 to 210 days.
<br />This unit is 40 percent relatively undisturbed Chapman
<br />loam, 5 percent disturbed Chapman loam, and 40
<br />percent Urban land. The components of this unit are so
<br />intricately intermingled that it was not practical to map
<br />them separately at the scale used.
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