LOCATION OVALL WA

Established Series
Rev. SBC/RJE
06/2011

OVALL SERIES

The Ovall series consists of moderately deep, well drained soils formed in glacial drift mixed with residuum and colluvium from andesite and breccia. These soils are on glaciated foothills and mountains with slopes of 0 to 75 percent. The average annual precipitation is about 50 inches, and the mean annual temperature is about 51 degrees F.

TAXONOMIC CLASS: Loamy-skeletal, isotic, mesic Andic Humixerepts

TYPICAL PEDON: Ovall gravelly ashy loam - on a southeast facing 28 percent slope under coniferous forest at 740 feet elevation. (Colors are for moist soil unless otherwise stated. All textures are apparent field textures.)

Oi--0 to 3 inches; partially decomposed needles, leaves, and twigs.

Oa--3 to 4 inches; highly decomposed forest litter; abrupt smooth boundary.

A1--4 to 8 inches; very dark brown (10YR 2/2) gravelly ashy loam, dark grayish brown (10YR 4/2) dry; strong fine subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; many very fine, fine, and medium roots, common coarse roots; many very fine interstitial pores; 25 percent rounded and subangular pebbles, 2 percent cobbles; slightly acid (pH 6.4); clear smooth boundary. (3 to 9 inches thick)

A2--8 to 16 inches; dark brown (10YR 3/3) gravelly ashy loam, brown (10YR 5/3) dry; moderate fine subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; many very fine, fine, and medium roots; many very fine interstitial pores; 25 percent rounded and subangular pebbles, 5 percent cobbles; slightly acid (pH 6.2); clear smooth boundary. (4 to 12 inches thick)

Bw1--16 to 25 inches; brown (10YR 4/3) very gravelly ashy loam, pale brown (10YR 6/3) dry; moderate fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine, fine, and medium roots; many very fine interstitial pores; 35 percent rounded and subangular pebbles, 10 percent cobbles; moderately acid (pH 5.8); gradual smooth boundary. (7 to 19 inches thick)

Bw2-- 25 to 38 inches; brown (10YR 4/3) very gravelly ashy loam, pale brown (10YR 6/3) dry; weak fine subangular blocky structure; slightly hard, friable slightly sticky and slightly plastic; common very fine and fine roots; common very fine interstitial pores; 45 percent rounded and subangular pebbles, 10 percent cobbles; moderately acid (pH 5.8); clear wavy boundary. (6 to 15 inches thick)

2R--38 inches; slightly weathered andesite.

TYPE LOCATION: King County, Washington; about 2.5 miles southwest of Issaquah via State Highway 900, then northeast on 185th Ave. S.E. to old logging road; 2,100 feet south and 2,100 feet east of the northwest corner of sec. 6, T. 23 N., R. 6 E., W.M.

RANGE IN CHARACTERISTICS: These soils are usually moist, but are dry in the moisture control section for 60 to 75 consecutive days. Depth to bedrock ranges from 20 to 40 inches. The mean annual soil temperature is 52 to 54 degrees F. The particle-size control section is 10 to 15 percent clay. Rock fragments in the particle-size control section range from 35 to 60 percent by volume and are dominantly rounded. The umbric epipedon is 10 to 20 inches thick. Reaction is strongly acid to slightly acid throughout.

The A horizon has hue of 7.5YR or 10YR, value of 2 through 4 moist, 4 through 6 dry; and chroma of 1 through 3 moist or dry. It contains 15 to 30 percent pebbles and 0 to 5 percent cobbles.

The Bw horizon has hue of 7.5YR, or 10YR moist or dry, value of 3 through 5 moist, 5 to 6 dry; and chroma of 2 through 4 moist or dry. Textures are very gravelly loam or very gravelly sandy loam. This horizon contains 30 to 45 percent pebbles and 0 to 15 percent cobbles.

Some pedons have a C horizon, which has colors and textures similar to the B horizon, and is massive.

COMPETING SERIES: These are the Coyota and Decy series. Coyota and Decy soils have more than 15 percent clay in the particle-size control section.

GEOGRAPHIC SETTING: Ovall soils are on glaciated foothills and mountains on the west slopes of the Cascade Mountains. Slopes are 0 to 75 percent. Elevations range from 500 to 1,800 feet. These soils formed in glacial drift mixed with residuum and colluvium from andesite and breccia. The climate is marine influenced, with cool, moist winters and relatively cool, dry summers. The mean January temperature is 37 degrees F; mean July temperature is 63 degrees F; and the mean annual temperature is 51 degrees F. Average annual precipitation is 45 to 60 inches. The frost-free season (32 degrees F) is 140 to 160 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Alderwood, Barneston, Beausite, Buckley, Mashel, Seattle, and Wilkeson soils. Alderwood soils have an ortstein layer at depths of 20 to 40 inches. Barneston soils are sandy-skeletal. Beausite soils have a spodic horizon. Buckley soils have an aquic moisture regime and are fine-loamy. Mashel soils have an argillic horizon and more than 35 percent clay in the control section. Seattle soils are Histosols and are very poorly drained. Wilkeson soils have an argillic horizon and are fine-loamy.

DRAINAGE AND PERMEABILITY: Well drained, slow to medium runoff; moderately rapid permeability.

USE AND VEGETATION: Timber production, watershed, wildlife habitat, and recreation are the principal uses. A few small areas are used for homesites and pasture. The native vegetation is Douglas-fir, western hemlock, western redcedar, red alder, and bigleaf maple. Understory species include salal, Oregon-grape, western swordfern, western brackenfern, Pacific dogwood, vine maple, red huckleberry, and creambush oceanspray.

DISTRIBUTION AND EXTENT: West slopes of the Cascade Mountains in King and Pierce Counties, Washington; MLRA 2. The series is of small extent.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon

SERIES ESTABLISHED: King County, Washington, 1971.

REMARKS: Diagnostic horizons and features recognized in this pedon are;
umbric epipedon from the mineral surface to 12 inches
cambic horizon from 12 to 34 inches
lithic contact at 34 inches.
The particle-size control section (from 10 to 34) averages 49 percent rock fragments.

National Cooperative Soil Survey
U.S.A.