LOCATION RACAS CO
Tentative Series
PRR, KLS
02/2025
RACAS SERIES
Depth class: Deep and very deep
Drainage class: Well and moderately well drained
Saturated hydraulic conductivity: Moderately low
Parent material: Thick and very thick clayey human-transported material over loess derived from glaciofluvial sources or human-transported material over slope alluvium derived from loess.
Geomorphic location: Human-transported fill on loess-mantled plains and storm-water retention basins and depressions on floodways within loess-mantled plains
Slope range: 0 to 10 percent
Mean annual temperature: 11.0 degrees C (51.8 degrees F)
Mean annual precipitation: 406 millimeters (16.0 inches)
Taxonomic Class:
Fine, spolic, smectitic, calcareous, mesic Torrertic Ustorthents
Typical Pedon:
Racas clay loam in urban, park. (Colors are for dry soil unless otherwise noted.)
^A--0 to 5 cm; dark grayish brown (10YR 4/2) clay loam, dark brown (10YR 3/3) moist; weak fine granular structure; slightly hard, friable, moderately sticky, moderately plastic; many very fine and fine roots, finely disseminated free carbonates throughout the matrix; slightly effervescent, moderately alkaline (pH 8.0); clear smooth boundary.
^C1--5 to 22 cm; brown (10YR 4/3)clay loam, dark brown (10YR 3/3) moist; massive; slightly hard, friable, moderately sticky, moderately plastic; many very fine and fine roots; finely disseminated free carbonates throughout the matrix; 2 percent gravel; 2 percent parachanners of shale; strongly effervescent; moderately alkaline (pH 8.2); clear smooth boundary.
^C2--22 to 54 cm; brown (10YR 5/3)silty clay, brown (10YR 4/3) moist; massive; moderately hard, firm, very sticky, very plastic; few fine roots; finely disseminated free carbonates and 3 percent carbonate masses (assumed to have been inherited from the fill) throughout the matrix; 2 percent gravel; 5 percent parachanners of shale; strongly effervescent; moderately alkaline (pH 8.4); clear smooth boundary.
^C3--54 to 114 cm; brown (10YR 5/3)clay loam, brown (10YR 4/3) moist; massive; slightly hard, friable, moderately sticky, slightly plastic; few fine roots; finely disseminated free carbonates throughout the matrix; 2 percent gravel; violently effervescent; moderately alkaline (pH 8.1); clear wavy boundary.
^2C1--114 to 161 cm; dark yellowish brown (10YR 4/4) silty clay, dark yellowish brown (10YR 3/4) moist; massive; moderately hard, firm, very sticky, very plastic; finely disseminated free carbonates throughout the matrix; very slightly effervescent; slightly alkaline (pH 7.6); gradual wavy boundary.
^2C2--161 to 200 cm; pale brown (10YR 6/3) silty clay loam, brown (10YR 4/3) moist; massive; slightly hard, friable, moderately sticky, moderately plastic; finely disseminated free carbonates throughout the matrix; violently effervescent; moderately alkaline (pH 8.1).
Type Location:
Denver County, CO
USGS Quadrangle: Englewood
Latitude: 39.7254028
Longitude: -104.9007722
Datum: WGS84
Coordinates sources: Hand-held GPS
Range in Characteristics:
Depth to free carbonates--0 to 200 centimeters
Thickness of human-transported material--50 to 200 centimeters
Particle-size control section (weighted average):
Clay content--35 to 45 percent
Sand content--15 to 30 percent
Total rock fragments--0 to 5 percent
^A or ^Au horizon:
Hue--7.5YR or 10YR
Value--3 to 5 dry; 1 to 4 moist
Chroma--3 to 5 dry; 2 to 4 moist
Texture (less than 2 mm fraction)--Silty clay loam, clay loam, loam
Clay content--28 to 45 percent
Rock fragments--0 to 15 percent gravel
Artifacts--0 to 5 percent
Calcium carbonate equivalent--0 to 5 percent
Reaction--pH 7.2 to 7.8
Thickness--10 to 35 centimeters
^C horizon(s):
Hue--7.5YR or 10YR
Value--4 to 6 dry; 3 to 5 moist
Chroma--3 to 5; moist or dry
Texture (less than 2 mm fraction)--Silty clay loam, silty clay, clay
Clay content--35 to 50 percent
Rock fragments--0 to 10 percent gravel
Calcium carbonate equivalent--5 to 14 percent
Reaction--pH 7.9 to 8.6
Thickness--15 to 50 centimeters
^Cu horizon(s) (where present):
Hue--10YR
Value--3 to 5 dry; 3 or 4 moist
Chroma--3 or 4 dry; 3 to 5 moist
Texture (less than 2 mm fraction)--Silty clay loam, clay loam, clay
Clay content--35 to 45 percent
Rock fragments--0 to 20 percent gravel
Artifacts--1 to 5 percent
Calcium carbonate equivalent--0 to 10 percent
Reaction--pH 7.2 to 8.2
Thickness--15 to 55 centimeters
2C horizon (when present):
Hue--7.5YR or 10YR
Value--4 to 6 dry; 3 or 4 moist
Chroma--4 or 5 dry; 2 to 5 moist
Texture (less than 2 mm fraction)--Silty clay loam, sandy clay loam
Clay content--28 to 40 percent
Rock fragments--0 to 3 percent gravels
Calcium carbonate equivalent--5 to 14 percent
Reaction--pH 7.9 to 8.4
Thickness--15 to 45 centimeters
Competing Series:
There are currently no competing series.
Geographic Settings:
Parent material--Thick and very thick clayey human-transported material over loess derived from glaciofluvial sources or human-transported material over slope alluvium derived from loess.
Landform--Human-transported fill on loess-mantled plains and storm-water retention basins and depressions on floodways within loess-mantled plains
Slope ranges--0 to 10 percent
Mean annual air temperature-10.0 to 12.0 degrees C (50.0 to 53.6 degrees F)
Mean annual precipitation range--356 to 432 millimeters (14.0 to 17.0 inches)
Frost-free period--135 to 165 days
Elevation--1,580 to 1,720 meters (~5,185 to 5,645 feet)
Climate--continental, temperate, semi-arid; very cold and snowy winters; cool, moist springs, hot summers, with North American monsoon precipitation from July through August.
Geographically Associated Soils:
Elyria soils: Found in similar landscape positions, but on mixed eolian deposits with a fine-loamy particle size control section;
Globeville soils: Found in depressions and storm-water retention basins on floodways within the loess-mantled hills, have a fine-loamy particle size control section; Manzanst soils: Found on adjacent pediments at the base of loess-mantled hills with less than 50 percent human-transported material; Rosegully soils: Found on floodplain steps along drainages in loess-mantled hills and have a fine-loamy particle size control section.
Drainage and Saturated Hydraulic Conductivity:
Drainage class: Well and moderately well drained
Saturated hydraulic conductivity: Moderately low (0.5 to 1.5 m/sec)
Flooding: Some Racas soils are subject to very rare flooding from March through August
Ponding: Some Racas soils are subject to ponding from March through August
Use and Vegetation:
Most areas are primarily used for urban development. The potential native vegetation is fourwing saltbush, winterfat, western wheatgrass, and blue grama.
Distribution and Extent:
Loess-mantled plains, primarily on the east bank of the South Platte River near Denver, CO; small extent in north-central Colorado; MLRA 67B.
Soil Survey Region (SSR) Responsible:
Bozeman, Montana
Series Proposed:
Denver County, CO 2025. Racas series is a coined name associated with an acronym for the Denver Soil Survey inventory protocol.
Remarks:
Typical Pedon Taxonomic Features:
Ochric epipedon--0 to 5 centimeters (^A horizon)
Free carbonates--0 to 200 centimeters (All horizons)
Human-transported materials--0 to 114 centimeters (^A, ^C1, ^C2, ^C3 horizons)
Lithologic discontinuity--114 centimeters
Particle-size control section--25 to 100 centimeters
Taxonomic version: Keys to Soil Taxonomy, 13th edition, (2022)
National Cooperative Soil Survey
U.S.A.