LOCATION BECHTEL                 ID

Established Series
Rev. CJW-SHB-JAL
01/2023

BECHTEL SERIES

The Bechtel series consists of deep, well drained soils on foothills. They formed in material weathered from siltite of the Libby, Wallace and Prichard formations and fine grained quartzites of the Striped Peak formation of the Belt supergroup with a mixed mantle of loess and volcanic ash. Permeability is moderately slow. Slope ranges from 20 to 40 percent. The average annual air temperature is about 44 degrees F and average annual precipitation is about 38 inches.

TAXONOMIC CLASS: Fine-loamy, mixed, superactive, frigid Vitrandic Hapludalfs

TYPICAL PEDON: Bechtel ashy silt loam, forestland; on a southeast facing slope of 28 percent at 3,140 feet elevation. When described on May 15, 1984, the soil was moist throughout. (Colors are for dry soil unless otherwise stated).

Oi--0 to 0.5 inch; slightly decomposed needles, leaves, and twigs.

A--0.5 to 5 inches; pale brown (10YR 6/3) ashy silt loam, brown (10YR 4/3) moist; weak fine subangular blocky structure parting to moderate fine granular; slightly hard, friable, nonsticky and slightly plastic; many very fine, fine, and common medium and coarse roots; many very fine and fine tubular pores; 5 percent gravel; slightly acid (pH 6.2); clear wavy boundary. (2 to 5 inches thick)

BA--5 to 12 inches; very pale brown (10YR 7/3) ashy silt loam, brown (10YR 5/3) moist; weak fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine and fine, few medium and coarse roots; common very fine and fine tubular pores; common fine brownish yellow (10YR 6/6) iron stains; 10 percent gravel; moderately acid (pH 6.0); gradual wavy boundary. (4 to 7 inches thick)

Bt1--12 to 20 inches; very pale brown (10YR 7/3) gravelly loam, brown (10YR 5/3) moist; moderate fine and medium subangular blocky structure; hard, firm, slightly sticky and slightly plastic; common very fine, fine, and few medium roots; common very fine and fine tubular pores; common faint clay films on faces of peds and lining pores; common fine brownish yellow (10YR 6/6) iron stains; 15 percent gravel; slightly acid (pH 6.5); gradual wavy boundary. (8 to 11 inches thick)

Bt2--20 to 33 inches; very pale brown (10YR 7/4) gravelly loam, yellowish brown (10YR 5/4) moist; moderate medium and coarse subangular blocky structure; hard, firm, moderately sticky and moderately plastic; common very fine, fine, and few medium roots; few very fine and fine tubular pores; common faint clay films on faces of peds and lining pores; 30 percent gravel; moderately acid (pH 6.0); gradual wavy boundary. (9 to 19 inches thick)

BC--33 to 47 inches; mixed very pale brown (10YR 8/3) and pale yellow (2.5Y 8/4) very gravelly loam, pale brown (10YR 6/3) and light yellowish brown (2.5Y 6/4) moist; weak medium and coarse subangular blocky structure; slightly hard, friable, slightly sticky and moderately plastic; few very fine and fine roots; few very fine and fine tubular pores; few fine brownish yellow (10YR 6/6) iron stains concentrated near boundary of Cr horizon; 50 percent gravel; strongly acid (pH 5.5); clear wavy boundary. (10 to 21 inches thick)

Cr--47 inches; soft siltstone with fractures greater than 4 inches apart.

TYPE LOCATION: Benewah County, Idaho; about 0.75 mile northwest of Emida, about 1500 feet north and 400 feet east of the southwest corner of section 28, T.44 N., R.2 W. Latitude 47 degrees 07 minutes 40 seconds N.; Longitude 116 degrees 36 minutes 15 seconds W.; NAD 83; Lindstrom Peak USGS topographic quadrangle.

RANGE IN CHARACTERISTICS:

Depth to bedrock - 40 to 60 inches
Solum thickness - 40 to 56 inches
Ochric epipedon - 9 to 12 inches thick
Moisture control section - dry August to mid-September (25 to 45 days); moist mid-September through July (udic moisture regime)
Average annual soil temperature - 44 to 46 degrees F
Average summer soil temperature - 49 to 54 degrees F with an O horizon (frigid temperature regime)

Volcanic ash influence 7 to 11 inches thick
Volcanic glass content in the 0.02 to 2 mm fraction - 5 to 20 percent
Acid-oxalate extractable Al + 1/2 Fe - 0.4 to 1.0 percent (estimated)
Moist bulk density - 1.2 to 1.4 g/cc (estimated)

A horizon
Value - 5 or 6 dry and 3 or 4 moist
Chroma 2 or 3 dry or moist
Texture Ashy-SIL, Ashy-L
Gravel content - 0 to 15 percent
Clay content 10 to 15 percent
Reaction - slightly acid or neutral

BA horizon
Value - 6 or 7 dry, 4 or 5 moist
Chroma 2 or 3 dry or moist
Texture Ashy-SIL, Ashy-L
Gravel content - 0 to 15 percent
Clay content - 10 to 15 percent
Reaction - moderately acid or slightly acid

Bt horizon
Value - 6 or 7 dry and 4 to 6 moist
Chroma 3 or 4 dry or moist
Texture - SIL, L, GR-L, GR-SIL, GRV-L
Gravel content - 5 to 30 percent in the upper part; 35 to 50 percent in the lower part
Paragravel content 0 to 10 percent
Cobble content - 0 to 5 percent lower part
Clay content - 15 to 26 percent, averages greater than 18 percent in the particle-size control section
Base saturation - 35 to 50 percent
Reaction - strongly acid to slightly acid

BC horizon
Hue 10YR or 2.5Y
Value 7 or 8 dry, 5 or 6 moist
Chroma 3 or 4 dry or moist
Texture GRV-L, GRX-L, CBX-L, GR-L, GR-SIL, GRV-SIL, CBV-L, CBV-SIL
Gravel content 15 to 80 percent
Cobble content 0 to 40 percent
Paragravel content 0 to 15 percent
Clay content -10 to 23 percent
Clay films present in some pedons on rock fragments

COMPETING SERIES: These are the Christoff, Keeler and Sly series.

Christoff soils: moderately well drained; E horizons with more than 60 percent volcanic ash and 5 to 10 percent hard weathered cinders; have 2E and 2Bt horizons with 5 to 15 percent gravel from breccia and tuffaceous rocks.

Keeler soils: greater than 60 inches to bedrock; 2Bt horizons with sandy loam or sandy clay loam textures derived from granite.

Sly soils: greater than 60 inches to bedrock; 2Bt horizons with silty clay loam textures and 25 to 38 percent clay; derived from basalt.

Soils with a similar classification
Placer soils: isotic mineralogy; 2Bt horizons with 5YR or 7.5YR hue and pararock and rock fragments of basalt origin.

GEOGRAPHIC SETTING: Bechtel soils are on south, east, and west facing convex foothills. Slopes range from 20 to 40 percent. These soils formed in material weathered from siltite of the Libby, Wallace and Prichard formations and fine grained quartzites of the Striped Peak formation of the Belt supergroup with a mantle of loess and minor amounts of volcanic ash. Elevations range from 2,800 to 3,500 feet. The average annual air temperature ranges from 43 to 45 degrees F, average annual precipitation is 30 to 40 inches, and frost-free season is from 90 to 120 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Ahrs, Helmer, Hobnail, Honeyjones, and Reggear soils. Ahrs soils are on mountains, and are loamy-skeletal and lack argillic horizons. Helmer and Reggear soils are on terraces, and have a fragipan and are moderately well drained. Hobnail soils are on terraces and are moderately well drained. Honeyjones soils are on north-facing mountains, and are ashy over loamy-skeletal and very deep.

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

USE AND VEGETATION: These soils are used for timber production, livestock grazing, wildlife habitat, recreation, and a few areas for homesites. Potential natural vegetation is mainly grand fir, Douglas-fir, western white pine, ponderosa pine, lodgepole pine, and western larch, with an understory of myrtle pachystima, queencup beadlily, baldhip rose, common snowberry, longtube twinflower, piper anemone, American trailplant, goldthread, Columbia brome, and sedge.

DISTRIBUTION AND EXTENT: Northern Idaho. This soil is not extensive.

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

SERIES ESTABLISHED: St. Joe Area, Shoshone County, Idaho, 1993.

REMARKS: Diagnostic horizons and features recognized in this pedon are:

Ochric epipedon - the zone from the mineral soil surface to 12 inches (A and BA horizons)

Argillic horizon - the zone from 12 to 33 inches (Bt1 and Bt2 horizons)

Volcanic ash influence the zone from the mineral soil surface to 12 inches (A and BA horizons)

Particle-size control section - the zone from 12 to 32 inches (Bt1 and part of Bt2 horizon)

ADDITIONAL DATA: Partial laboratory data available for Soil Survey Sample Number: 91ID009-001, NSSL Pedon Number: 92P0274 Benewah County, Idaho.

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National Cooperative Soil Survey
U.S.A.