LOCATION SWINOMISH WAEstablished Series
TAXONOMIC CLASS: Ashy over loamy-skeletal, amorphic over isotic, mesic Aquic Vitrixerands
TYPICAL PEDON: Swinomish gravelly loam -forested. (Colors are for moist soils unless otherwise noted. All textures are apparent field textures.)
01--1 inch to 0; needles, leaves and twigs.
A1--0 to 3 inches; dark brown (7.5YR 3/2) gravelly loam, brown (7.5YR 5/2) dry; weak fine granular structure; soft, very friable, nonsticky and slightly plastic; weakly smeary; common very fine and fine roots; 15 percent pebbles and 5 percent cobbles; NaF pH l0.5; slightly acid (pH 6.5); clear smooth boundary. (0 to 4 inches thick)
B21--3 to 11 inches; strong brown (7.5YR 4/6) gravelly loam, reddish yellow (7.5YR 6/6) dry; weak coarse subangular blocky structure; soft, very friable, nonsticky and slightly plastic; weakly smeary; common very fine, fine, medium, and coarse roots; 20 percent pebbles and 5 percent cobbles; NaF pH 11.0; clear smooth boundary. (6 to 12 inches thick)
B22--11 to 20 inches; strong brown (7.5YR 5/6) gravelly loam, light yellowish brown (10YR 6/4) dry; weak medium subangular blocky structure; soft, very friable, nonsticky and slightly plastic, weakly smeary; common fine, medium and coarse roots; 15 percent pebbles and 5 percent cobbles; NaF pH 10.5; slightly acid (pH 6.5); clear smooth boundary. (6 to 12 inches thick)
B3--20 to 24 inches; yellowish brown (10YR 5/4) very gravelly fine sandy loam, light yellowish brown (2.5Y 6/4) dry; weak fine subangular blocky structure; soft, very friable, nonsticky and nonplastic; weak smeary, common fine, medium and coarse roots; 25 percent pebbles and 10 percent cobbles; NaF pH 11.0; slightly acid (pH 6.2); clear smooth boundary. (2 to 8 inches thick)
C1--24 to 29 inches; light olive brown (2.5Y 5/4) very gravelly fine sandy loam, light yellowish brown (2.5Y 6/4) dry; massive; soft, very friable, nonsticky and nonplastic; common fine, medium and coarse roots; 50 percent pebbles; NaF pH 11.0; slightly acid (pH 6.2); abrupt smooth boundary. (3 to 7 inches thick)
C2--29 to 31 inches; light olive brown (2.5Y 5/4) very gravelly, sandy loam, light yellowish brown (2.5Y 6/4) dry; common fine distinct yellowish red (5YR 5/8) mottles; massive; soft, very friable, nonsticky and nonplastic; few fine, medium and coarse roots; 60 percent pebbles; NaF pH ll.0; slightly acid (pH 6.2); abrupt smooth boundary. (2 to 4 inches thick)
C3r--31 to 60 inches; olive gray (5Y 5/2) dense glacial till that breaks to very gravelly sandy loam; light gray (5Y 7/2) dry; massive; hard, firm, nonsticky and nonplastic; 50 percent pebbles; slightly acid (pH 6.2)
TYPE LOCATION: Skagit County, Washington; 260 feet north and 2,620 feet east of SW corner sec. 26, T. 34 N., R. 2 E.
RANGE IN CHARACTERISTICS: Depth to the paralithic contact with dense glacial till is 25 to 40 inches. These soils are usually moist but are dry in the moisture control section for 75 to 90 days following the summer solstice. base saturation is 35 to 75 percent throughout the control section. Coarse fragments in the control section average from 35 to 50 percent and consist of pebbles and cobbles. The mean annual soil temperature is estimated to range from 48 to 52 degrees F. Reaction is slightly acid or neutral.
The A horizon has hue of 7.5YR and 10YR, value of 2 or 3 moist, 5 or 6 dry, and chroma of 2 or 3 moist and dry.
The B horizon has hue of 5YR, 7.5YR or 10YR, value of 4 or 5 moist, 6 or 7 dry, and chroma of 4 through 6 moist and dry. It is gravelly loam, very gravelly sandy loam, or very gravelly fine sandy loam.
The B3 horizon has hue of 10YR or 2.5Y, value of 5 or 6 moist and dry, and chroma of 3 or 4 moist and dry. It is very gravelly fine sandy loam or very gravelly sandy loam.
The C horizon has hue of 10YR or 2.5Y, value of 5 or 6 moist, 6 or 7 dry, and chroma of 3 or 4 moist and dry. It is very gravelly sandy loam or very gravelly fine sandy loam.
The Cr horizon consists of dense glacial till that breaks to very gravelly sandy loam or very gravelly loamy fine sand.
COMPETING SERIES: These are the Blethen, Heisler, Lyre, Neer, Ogarty, Pickett, Squires, and Vanzandt series. Blethen, Heisler and Lyre soils lack a paralithic contact within depths of 60 inches. Neer soils have base saturation of 10 to 20 percent in the B horizon, and contain shot- like pebbles throughout the control section. Ogarty, Pickett and Squires soils are 20 to 40 inches deep to a lithic contact. Vanzandt soils are dry in the moisture control section for 60 to 75 consecutive days.
GEOGRAPHIC SETTING: Swinomish soils are on glaciated uplands at elevations of l00 to 1,200 feet. Slopes are 0 to 30 percent. They formed in glacial till with an admixture of loess and volcanic ash. These soils have a mild marine climate with cool dry summers and cool moist winters. Average annual precipitation is 20 to 30 inches. Average January temperature is about 36 degrees F. and average July temperature is about 64 degrees F. and mean annual temperature is about 50 degrees F. Frost-free season is 160 to 210 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Clallam and LaConner soils. Clallam soils are loamy-skeletal. LaConner soils lack a cambic horizon and are sandy-skeletal.
DRAINAGE AND PERMEABILITY: Moderately well drained; medium to slow runoff; moderate permeability above the dense glacial till layer and very slow in the dense glacial till.
USE AND VEGETATION: Swinomish soils are used for woodland, urbanland, and recreation land. Native vegetation is Douglas-fir, grand fir, western redcedar, western swordfern, trailing blackberry, and Indian plum.
DISTRIBUTION AND EXTENT: Western Skagit County, Washington. This series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Skagit County, Washington, 1981.
REMARKS: Classification only changed 4/94 because of recent amendments to Soil Taxonomy. Estimate glass content at 5 to 20 percent and acid-oxalate extract of 1.0 to 2.0 percent from 0 to 20 inches.