LOCATION SCOAP                   WA

Established Series
Rev. NCD-BDG-RJS
05/2017

SCOAP SERIES

The Scoap series consists of very deep, well drained soils influenced by loess and volcanic ash at the surface and formed in colluvium, outwash and till. Scoap soils are on glaciated uplands, outwash terraces and mountain slopes. Slopes are 5 to 65 percent. Mean annual precipitation is about 20 inches, and mean annual air temperature is about 6.7 degrees C.

TAXONOMIC CLASS: Loamy-skeletal, isotic, frigid Vitrandic Haploxerolls

TYPICAL PEDON: Scoap gravelly ashy loam - woodland. (Colors are for dry soil unless otherwise stated.)

Oi--0 to 5 cm; black (10YR 2/1) moist; loose, partially decomposed organic litter, composed of needles, leaves, twigs, bark and cones; slightly acid (pH 6.4); abrupt smooth boundary. (5 to 10 cm thick)

A1--5 to 23 cm; dark grayish brown (10YR 4/2) gravelly ashy loam, very dark brown (10YR 2/2) moist; weak fine and medium granular structure; slightly hard, friable, slightly sticky and slightly plastic; common fine and medium, and few coarse roots; common fine pores; 25 percent gravel; neutral (pH 6.6); clear wavy boundary. (13 to 20 cm thick)

A2--23 to 38 cm; grayish brown (10YR 5/2) gravelly ashy loam, very dark grayish brown (10YR 3/2) moist; weak fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common fine and medium, and few coarse roots; common fine pores; 25 percent gravel; slightly acid (pH 6.4); clear wavy boundary. (13 to 33 cm thick)

Bw1--38 to 71 cm; brown (10YR 5/3) gravelly loam, dark brown (10YR 3/3) moist; weak fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common fine and medium, and few coarse roots; common fine pores; 25 percent gravel; slightly acid (pH 6.4); clear wavy boundary.

Bw2--71 to 89 cm; pale brown (10YR 6/3) very cobbly loam, dark yellowish brown (10YR 3/4) moist; weak fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common fine and medium, and few coarse roots; common fine pores; 20 percent gravel and 30 percent cobbles; slightly acid (pH 6.4); clear wavy boundary. (combined thickness of Bw1, Bw2 -- 22 to 58 cm)

BC--89 to 114 cm; light yellowish brown (10YR 6/4) very cobbly loam, dark yellowish brown (10YR 3/4) moist; massive; hard, friable, slightly sticky and slightly plastic; common fine and medium, and few coarse roots; common fine pores; 20 percent gravel and 30 percent cobbles; slightly acid (pH 6.4); clear wavy boundary. (18 to 44 cm thick)

C--114 to 152 cm; very pale brown (10YR 7/4) very stony loam, brown (10YR 4/3) moist; massive; hard, friable, slightly sticky and slightly plastic; few fine, medium and coarse roots; few fine pores; 10 percent gravel, 15 percent cobbles and 25 percent stones; slightly acid (pH 6.4).

TYPE LOCATION: Stevens County, Washington; about 4.8 kilometers southeast of Gifford; 425 meters south and 700 meters east of the northwest corner of sec. 12, T. 32 N., R. 37 E.; W.M.. Latitude - 48 degrees, 17 minutes, 25.14 seconds N; Longitude - 118 degrees, 5 minutes, 50.08 seconds W. NAD 83; USGS topographic quadrangle, Wellington Peak, WA.

RANGE IN CHARACTERISTICS:
Mean annual soil temperature -- 6.7 to 8.0 degrees C.
Mollic epipedon -- 50 to 75 cm thick
Soil moisture control section -- usually moist but dry in all parts for 60 to 75 consecutive days following the summer solstice.

Vitrandic feature
Thickness -- 25 to 50 cm
Moist bulk density -- 1.20 to 1.50 g/cc
Volcanic glass content -- 5 to 20 percent
Acid-oxalate extractable Al plus 1/2 of the acid-oxalate extractable Fe -- 0.4 to 1.0 percent
15-bar water retention -- 5 to 12 percent for air dried samples.

Control section
Clay -- 8 to 12 percent
Rock fragments -- averages 35 to 50 percent

Base saturation (by sum of cations) -- assumed to be less than 75 percent in some part between 25 and 75 cm

A1, A2 horizons
Value: 4 or 5 dry; 2 or 3 moist
Chroma: 1 to 3 dry and moist
Texture (less than 2mm fraction): ashy silt loam, ashy loam or ashy sandy loam
Rock fragments: 5 to 40 percent gravel
Reaction: neutral or slightly acid

Bw1, Bw2, BC horizons
Value: 4 to 6 dry; 3 or 4 moist
Chroma: 3 or 4 dry and moist
Texture (less than 2mm fraction): loam, sandy loam or silt loam
Rock fragments: 20 to 50 percent gravel; 0 to 30 percent cobbles
Reaction: neutral or slightly acid

C horizon
Value: 5 to 7 dry: 3 to 5 moist
Chroma: 3 or 4 dry and moist
Texture (less than 2mm fraction): loam, loamy sand or sandy loam
Rock fragments: 10 to 50 percent gravel; 5 to 40 percent cobbles and stones
Reaction: neutral or slightly acid

COMPETING SERIES:
Bearspring (WA): have a mollic epipedon less than 50 cm thick
Bigelk (OR): have a mollic epipedon less than 50 cm thick
Cassal (WA): have redox features at 75 to 114 cm
Cherrycreek (OR): are moderately deep to a lithic contact
Deck (OR): are moderately deep to a lithic contact
Eastpine (OR): are deep to a lithic contact
Egyptcreek (OR): are moderately deep to a lithic contact
Fredonyer (CA): are moderately deep to a lithic contact
Golfer (OR): are moderately deep to a paralithic contact
Grubcreek (OR): are moderately deep to a lithic contact
Kettlecreek (OR): are deep to a lithic contact
Longs (ID): are deep to a lithic contact
Mccrosket (ID): are deep to a paralithic contact
Midpeak (WA): are moderately deep to a lithic contact
Mineral (WA): are moderately deep to a lithic contact
Peahke (OR): are moderately deep to a lithic contact
Piersonte (OR): have volcanic ash influence to 150 cm
Porch (OR): are moderately deep to a lithic contact
Shalrock (WA): are moderately deep to a lithic contact
Shilling (ID): have a mollic epipedon 25 to 50 cm thick
Umatilla (OR): have more than 25 percent clay in the particle-size control section
Webbgulch (OR): are moderately deep to a lithic contact
Yellcreek (WA): have a mollic epipedon 18 to 38 cm thick

GEOGRAPHIC SETTING: Scoap soils are on glaciated uplands, outwash terraces, and mountain slopes at elevations of 455 to 1,465 meters. Slopes are 5 to 65 percent. Soils are influenced by loess and volcanic ash at the surface, and formed in colluvium, outwash and till. Scoap soils are in a continental climate with warm, dry summers and cool, moist winters. Mean annual precipitation is 375 to 650 mm. Mean annual temperature is 5.0 to 7.2 degrees C. The frost-free season is 90 to 120 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Aits, Dehart, Donavan, Inkler, Maki, Raisio, Rufus, and Stevens soils. Aits, Donavan and Stevens soils are coarse-loamy. Dehart soils do not have a mollic epipedon and are on mountains. Aits soils are on glaciated mountains. Donavan soils are on toeslopes, footslopes, and backslopes of mountains. Inkler soils have an admixture of volcanic ash in the upper part of the particle-size control section with a bulk density of 0.85 to 0.95 g/cc and are on foothills and mountains. Maki and Raisio soils are 50 to 100 cm deep to a lithic contact and Maki soils are also calcareous. Maki soils are on south-facing glaciated uplands and mountain sides. Rufus soils are 25 to 50 cm deep to a lithic contact. Raisio, Rufus, and Stevens soils are on south-facing sideslopes and ridgetops of mountains.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained; moderately high saturated hydraulic conductivity.

USE AND VEGETATION: These soils are used primarily for timber production and grazing and some is used for dryland cropland and pasture. Potential natural vegetation includes Douglas-fir, ponderosa pine, and western larch with an understory of pinegrass, mallow ninebark, common snowberry, Oregon-grape, snowbrush ceanothus, creambush oceanspray, bluebunch wheatgrass, lupine and prairie junegrass.

DISTRIBUTION AND EXTENT: The series is of small extent in Eastern, Washington. MLRA 43A, 44A.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.

SERIES ESTABLISHED: Stevens County, Washington, 1978.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon -- 5 to 71 cm (A1, A2, Bw1 horizons)
Cambic horizon -- 71 to 89 cm (Bw2 horizon)
Vitrandic feature -- 5 to 38 cm (A1, A2 horizons)
Particle size control section -- the zone from 30 to 105 cm (part of the A2, Bw1, Bw2, part of the BC horizons)

Scoap soils should be further investigated to determine typical mineralogy (isotic vs. mixed).

Taxonomic version: Keys to Soil Taxonomy, Twelfth Edition, 2014.

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National Cooperative Soil Survey
U.S.A.