LOCATION GROTTO WAEstablished Series
TAXONOMIC CLASS: Sandy-skeletal, mixed, frigid Typic Haplorthods
TYPICAL PEDON: Grotto gravelly loamy sand, on a 4 percent river terrace in a mixed stand of Douglas-fir and western hemlock at 1,860 feet elevation. (Colors are for moist soil unless otherwise noted.)
01--2 to 1 inch; forest litter; undecomposed needles, bark, and twigs.
02--1 inch to 0; decomposed needles, twigs, and bark.
E--0 to 5 inches; brown (7.5YR 5/2) gravelly loamy sand, pinkish gray (7.5YR 7/2) dry; weak fine subangular blocky structure; soft, friable, nonsticky, nonplastic; many fine, common medium and coarse roots; many fine irregular pores; 30 percent pebbles; moderately acid (pH 5.9); clear smooth boundary. (2 to 7 inches thick)
Bhs--5 to 19 inches; dark brown (7.5YR 3/2) very gravelly coarse sand, brown (10YR 4/3) dry weak fine subangular blocky structure; common fine, medium, and coarse roots; many fine irregular pores; 40 percent pebbles; moderately acid (pH 5.9); clear wavy boundary. (11 to 25 inches thick)
Bs--19 to 36 inches; brown (10YR 4/3) and strong brown (7.5YR 5/6) very gravelly coarse sand, pale brown (10YR 6/3) and reddish yellow (7.5YR 7/6) dry; massive; hard in place, slightly hard to soft removed, firm in place, friable removed, nonsticky, nonplastic; common medium roots; many fine irregular pores; 45 percent pebbles; slightly acid (pH 6.21); clear smooth boundary. (0 to 18 inches thick)
C--36 to 60 inches; yellowish brown (10YR 5/4 and 10YR 5/6) very gravelly sand, light yellowish brown (10YR 6/4) and brownish yellow (10YR 6/6) dry; massive; hard in place, slightly hard removed, firm in place, friable removed, nonsticky, nonplastic; few medium roots; 55 percent pebbles; slightly acid (pH 6.4).
TYPE LOCATION: Snoqualmie Pass Area, King County, Washington; 2,400 feet south and 1,300 feet west of the northeast corner, sec. 10, T. 19 B., R. 9 E.
RANGE IN CHARACTERISTICS: These soils are usually moist but are dry in the moisture control section for 45 to 60 consecutive days following summer solstice. The average annual soil temperature ranges from 44 to 47 degrees F. The particle-size control section averages from 35 to 55 percent coarse fragments by volume. Some pedons lack an Oa horizon.
The E horizon has hue of 7.5YR or 10YR, value of 2 to 5 moist, 4 to 7 dry, and chroma of 1 to 3, moist or dry. It is strongly acid or very strongly acid.
The Bhs horizon has hue of 5YR, 7.5YR, or 10YR, value of 3 or 4 moist, 4 to 6 dry, and chroma of 2 to 6 moist or dry. The upper 3 inches has value and chroma of 2 or 3 moist. Coarse fragments range from 20 to 50 percent by volume. It is strongly acid or very strongly acid. Some pedons have weak thin platy structure.
The Bs horizon has hue of 7.5YR or 10YR, value of 3 to 5 moist and chroma of 3 to 6 moist or dry. Textures are loamy sand, sand, or coarse sand. Coarse fragments range from 35 to 60 percent by volume. It is moderately acid or slightly acid.
The C horizon has hue of 7.5YR, 10YR, or 2.5Y, value of 3 to 5 moist, 4 to 7 dry, and chroma of 2 to 6 moist and dry. It is very gravelly sand or very gravelly coarse sand. Coarse fragments range from 35 to 60 percent by volume. It is moderately acid or slightly acid.
COMPETING SERIES: These are the Colton, Etach, Guardlake, Hermon, Limking, Marblemount, Masardis, Sheepscot, Skykomish, Stetson, Teneriffe, and Waiska series. Colton, Guardlake, Hermon, Masardis, Sheepscot, Stetson, Teneriffe, and Waiska soils have a udic moisture regime. Etach soils are 20 to 40 inches deep to a paralithic contact with dense glacial till. Hermon, Limking, Sheepscot, and Skykomish soils are sandy loam in the fine earth fraction of the E and Bs horizons. Marblemount soils are 20 to 40 inches deep to bedrock. Teneriffe soils also are not stratified and have a mantle of volcanic ash 7 to 14 inches thick.
GEOGRAPHIC SETTING: Grotto soils are on river terraces and formed in alluvium. Elevations range from 1,600 to 2,800 feet. Slopes range from 0 to 8 percent. The climate is marine influenced wit cool, wet winters and cool, dry summers. Average annual precipitation ranges from 60 to 100 inches. The mean January temperature is about 33 degrees F, mean July temperature is about 60 degrees F, and the mean annual temperature is about 45 degrees F. The frost-free season is 130 to 160 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Skykomish soils and Rober soils. Rober soils are fine-silty.
DRAINAGE AND PERMEABILITY: Somewhat excessively drained; rapid permeability; slow runoff. These soils are subject to rare flooding.
USE AND VEGETATION: Used for timber production, watershed and wildlife habitat. Vegetation is western hemlock, Douglas-fir, western redcedar and red alder with an understory of vine maple, salal, Oregon-grape, red huckleberry, western swordfern, and western brackenfern.
DISTRIBUTION AND EXTENT: River valleys on the west slopes of the Cascade mountains in King and Pierce Counties, Washington. This soil is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Snoqualmie Pass Area, Washington, 1986.
REMARKS: Diagnostic horizons and features recognized in this pedon are: an albic horizon from the mineral surface to 5 inches; a spodic horizon from 5 to 19 inches; and a particle-size control section from 10 to 40 inches that is sandy throughout and averages 45 percent rock fragment.