LOCATION GREHALEM WAEstablished Series
TAXONOMIC CLASS: Fine-loamy, isotic, nonacid, isomesic Typic Udifluvents
TYPICAL PEDON: Grehalem silt loam - cultivated. (Colors are for moist soil unless otherwise noted.)
Ap--0 to 8 inches; dark brown (10YR 3/3) silt loam, light brownish gray (2.5Y 6/2) dry; moderate fine subangular blocky structure; hard, friable, moderately sticky and moderately plastic; many fine roots; very porous; moderately acid; clear smooth boundary. (7 to 9 inches thick)
C1--8 to 40 inches; dark brown (10YR 3/3) silty clay loam, pale yellow (2.5Y 7/4) dry; moderate fine subangular blocky structure; very hard, friable, moderately sticky and moderately plastic; common fine roots; very porous; thin loose sand and loamy sand lenses; moderately acid; gradual wavy boundary. (20 to 40 inches thick)
C2--40 to 80 inches; dark yellowish brown (10YR 4/4) silty clay loam, pale yellow (2.5Y 7/4) dry; weak medium subangular blocky structure; very hard, friable, moderately sticky and moderately plastic; very porous; thin loose sand and loamy sand lenses; moderately acid.
TYPE LOCATION: Grays Harbor County, Washington; 2 miles southeast of Copalis Crossing on State Highway 109; soil pit on H. N. Anderson Ranch, 100 feet south of cone spruce tree, 500 feet east of river bank in pasture; east 1/2, northwest 1/4, southwest 1/4 of section 4, T. 18 N., R. 11 W., W.M.
RANGE IN CHARACTERISTICS: Mean annual soil temperature is 47 degrees to 52 degrees F. The difference between the mean summer and mean winter soil temperature is 5 to 9 degrees F. The particle-size control section is dominantly silty clay loam and averages 27 to 35 percent clay. Thin sand to clay lenses occur throughout.
The A or Ap horizon has hue of 2.5Y or 5Y dry, value of 3 or 4 moist 6 dry, and chroma of 2 or 3 moist, 3 or 4 dry. It is loam or silt loam. It is weak or moderate granular or subangular blocky structure.
The C horizon has hue of 2.5Y or 5Y dry, value of 3 through 5 moist, 6 or 7 dry, and chroma of 3 or 4 moist and dry. It is silty clay loam but is stratified with thin lenses of sand, loamy sand, sandy loam and very fine sandy loam. It is weak to moderate subangular blocky structure or is massive. Some thin strata are single grained.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: These soils are on nearly level floodplains usually subject to annual stream overflow. Elevation ranges from sea level to 100 feet. The soils formed in medium and moderately fine textured alluvial deposits derived from basic igneous and sedimentary rocks. These soils occur in cool, coastal areas where the average annual precipitation ranges from 70 to 160 inches. Mean January temperature is 39 degrees F., mean July temperature is 60 degrees F., average annual temperature is 50 degrees F., and the growing season (28 degrees F.) is between 180 and 220 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Ocosta and Humptulips soils. Ocosta soils are poorly drained, strongly mottled, and are fine textured. Humptulips soils have sandy-skeletal material in the lower part of the particle-size control section.
DRAINAGE AND PERMEABILITY: Well drained; slow runoff; moderate permeability. Most of these soils are subject to annual stream overflow.
USE AND VEGETATION: Most of these soils are cleared and used for pasture, hay, or silage crops. Small uncleared areas have a forest cover of maple, red alder, and western hemlock with a dense understory of shrubs.
DISTRIBUTION AND EXTENT: Coastal floodplains of western Washington MLRA 4A. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Grays Harbor County, Washington, 1970.
Remarks: Diagnostic horizons and other features
Ochric epipedon:
Irregular decrease in organic matter with depth